Serum KL-6 levels predict the occurrence and severity of treatment-related interstitial lung disease in lung cancer

doi:10.21203/rs.3.rs-2887328/v1

Download PDF

Article

Serum KL-6 levels predict the occurrence and severity of treatment-related interstitial lung disease in lung cancer

https://doi.org/10.21203/rs.3.rs-2887328/v1

This work is licensed under a CC BY 4.0 License

Journal Publication

published 23 Oct, 2023

Read the published version in Scientific Reports →

You are reading this latest preprint version

This study aimed to investigate the feasibility of Krebs von den Lungen-6 (KL-6) as potential biomarker for treatment-related ILD (TR-ILD) in lung cancer. We recruited patients with lung cancer in whom serum KL-6 was measured for differentiating between pneumonia and ILD (category 1), diagnosing and assessing the severity of suspicious TR-ILD (category 2), or evaluating baseline levels before cancer treatment (category 3). Among 1297 patients who underwent KL-6 testing, 422 had lung cancer, and TR-ILD was detected in 194 patients. In lung cancer patients, median KL-6 level was higher in patients with drug-induced ILD than in those without ILD or those with radiation pneumonitis, and it was correlated with the severity of TR-ILD. Elevated serum KL-6 (cutoff: 449.9 U/mL) was an independent risk factor of severe TR-ILD, and elevated serum KL-6 with normal serum procalcitonin was associated with severe TR-ILD rather than non-ILD respiratory disease or non-severe TR-ILD. Patients with high serum KL-6 levels had worse overall survival compared with those with low serum KL-6 levels, regardless of patients’ categories. Therefore, serum KL-6 may be surrogate marker for predicting the occurrence and assessing the severity of TR-ILD at the time of suspicious ILD events and before lung cancer treatment.

Health sciences/Biomarkers/Diagnostic markers

Health sciences/Risk factors

Health sciences/Signs and symptoms/Respiratory signs and symptoms

Health sciences/Oncology/Cancer/Lung cancer

KL-6

interstitial lung disease

lung cancer

Lung cancer has been reported to have the highest mortality rates relative to other malignancies worldwide, including in South Korea ^1,2. However, the development of several robust therapeutic agents for treating cancer, such as targeted agents and immune checkpoint inhibitors (ICIs), has led to survival improvements for patients with advanced-stage lung cancer ³. These novel therapies also have led to survival benefits in non-advanced lung cancer. Adjuvant treatment with osimertinib, a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, was recently incorporated into the standard treatment of EGFR-mutated early-stage non-small cell lung cancer (NSCLC) ⁴. The successes of randomized clinical trials of anti-programmed death-1 (PD-1) or PD-ligand 1 (PD-L1) monoclonal antibodies have presented a new horizon of NSCLC treatment, with options for neoadjuvant treatment ⁵, adjuvant treatment ^6,7, and consolidation treatment after chemoradiation therapy (CRT) ⁸.

However, as survival rates and corresponding durations of treatment increase, lung cancer treatment can lead to additional long-term exposure to adverse events, especially pneumonitis. In one study, among patients with locally advanced NSCLC who received concurrent CRT (CCRT), 83% and 34% of patients developed pneumonitis and symptomatic pneumonitis, respectively ⁹. According to a real-world multi-institutional cohort study, 22% of patients who received PD-1/PD-L1 inhibitors suffered from pneumonitis, and patients with pneumonitis showed an increased risk of death (hazard ratio [HR]: 2.34, 95% confidence interval [CI]: 1.47–3.71). Therefore, minimizing treatment interruption necessitated by treatment-related side effects is crucial to improve treatment compliance and to extend treatment duration and survival. However, few studies have investigated and validated biomarkers for predicting the occurrence and severity of treatment-related interstitial lung disease (TR-ILD).

Krebs von den Lungen 6 (KL-6) is a mucinous high-molecular-weight glycoprotein expressed on the surfaces of type II alveolar epithelial cells. When the epithelial cell membranes of type II alveolar epithelial cells are damaged, KL-6 diffuses into the blood flow. This results in elevated serum KL-6 levels, which reflect the extent of damage and regeneration of type II pneumocytes ^10,11. According to a meta-analysis and a retrospective study, higher KL-6 levels correlate with more severe or acutely exacerbated ILD, making KL-6 a marker of poor prognosis ^12,13.

Based on the unmet need for developing biomarkers for treatment-related adverse events, this study aimed to evaluate the usefulness of KL-6 as a biomarker of TR-ILD during the treatment of lung cancer.

Baseline characteristics and serum KL-6 levels

The flow of patient enrollment and summary of baseline characteristics are presented in Fig. 1 and Table 1, respectively. We recruited 1297 patients who were tested with serum KL-6, among whom 422 patients (32.5%) had lung cancer. Of the patients without lung cancer, 674 (77.0%) had underlying ILD. Most patients (76.6%) were diagnosed with ILD at the time of their respective KL-6 tests, and acute exacerbations of (underlying) idiopathic ILD (98.5%) predominated. Serum KL-6 was mainly measured to diagnose and assess the severity of ILD (categories 1 and 2). Compared with individuals without lung cancer, the patients with lung cancer were younger (70.0 vs 73.0) and were more likely to be men. Most lung cancer patients (85.3%) had a smoking history, and 50.7% of the patients had underlying chronic obstructive pulmonary disease. More than half of the patients (57.8%) were diagnosed with stage-IV disease, and most patients had received CCRT (38.4%) or systemic chemotherapy (42.6%) as the initial lung cancer treatment. TR-ILD was detected in 194 patients (46.0%), and RP (61.3%) was the most common type of TR-ILD. The most common indication for serum KL-6 testing was the evaluation of baseline levels before lung cancer treatment that could cause TR-ILD (category 3).

Table 1

Baseline characteristics of patients with and without lung cancer.
Characteristic	Total (N = 1297)	Non-LC (n = 875)	LC (n = 422)	P-value
Age	71.0 (69.5–70.7)	73.0 (69.8–71.4)	70.0 (68.2–69.8)	0.005
Sex				< 0.001
Female	321 (24.7)	273 (31.2)	48 (11.4)
Male	976 (75.3)	602 (68.8)	374 (88.6)
Smoking				< 0.001
Never smoker	544 (41.9)	482 (55.1%)	62 (14.7)
Current smoker	279 (21.5)	126 (14.4%)	153 (36.3)
Ex-smoker	474 (36.5)	267 (30.5%)	207 (49.0)
Comorbidity
ILD	718 (55.4)	674 (77.0)	44 (10.4)	< 0.001
COPD	433 (33.4)	219 (25.0)	214 (50.7)	< 0.001
ECOG PS score				< 0.001
0	220 (17.0)	205 (23.4)	15 (3.5)
1	690 (53.2)	392 (44.8)	298 (70.6)
2	175 (13.5)	78 (8.9)	97 (23.0)
3	93 (7.1)	85 (9.7)	8 (1.9)
4	119 (9.2)	115 (13.1)	4 (1.0)
Pulmonary function
FEV1, L	2.16 (2.10–2.19)	2.30 (2.15–2.28)	1.80 (1.62–2.10)	0.008
FEV1, %	76.0 (74.79–77.74)	80.0 (78.87–82.82)	69.68 (58.68–73.55)	< 0.001
FVC, L	2.89 (2.85–2.97)	2.87 (2.79–2.96)	2.77 (2.46–2.96)	0.085
FVC, %	73.06 (71.32–73.74)	75.0 (71.89–75.35)	66.41 (60.86–71.36)	0.132
DLCO, %	65.0 (64.61–67.57)	62.0 (62.03–66.25)	73.88 (65.27–79.37)	0.005
Serum CEA	-	-	6.60 (8.64–73.40)	-
Serum CRP	7.76 (7.97–13.80)	8.71 (8.97–11.08)	6.83 (6.40-13.84)	0.602
Serum PCT	0.18 (0.23–0.47)	0.20 (1.05–3.39)	0.21 (0.22–0.51)	0.003
Initial diagnosis				-
Lung cancer	-	-	422 (100.0)
ILD	-	670 (76.6)	-
Pneumonia	-	154 (17.6)	-
Others	-	51 (5.8)	-
Histology				-
ADC	-	-	156 (37.0)
SQC	-	-	174 (41.2)
NSCLC, NOS	-	-	17 (4.0)
SCLC	-	-	75 (17.8)
Stage (TNM 8th )				-
Early (I-III, LD)	-	-	178 (42.2)
Advanced (IV, ED)	-	-	244 (57.8)
Driver mutation				-
EGFR (n = 191)	-	-	34 (17.8)
ALK (n = 186)	-	-	14 (7.5)
ROS1 (n = 166)	-	-	2 (1.2)
PD-L1 IHC (SP263) (n = 312)				-
TPS < 1%	-	-	120 (38.6)
TPS ≥ 1%, < 50%	-	-	90 (28.8)
TPS ≥ 50%	-	-	102 (32.6)
PD-L1 IHC (22C3) (n = 157)				-
TPS < 1%	-	-	39 (24.8)
TPS ≥ 1%, < 50%	-	-	56 (35.7)
TPS ≥ 50%	-	-	62 (39.5)
Initial therapy of LC				-
Operation	-	-	59 (14.0)
CCRT	-	-	162 (38.4)
Systemic chemotherapy	-	-	180 (42.6)
SBRT or RT alone	-	-	12 (2.8)
Palliative treatment	-	-	3 (0.7)
Supportive care	-	-	6 (1.4)
IrAE (n = 270)			53 (19.6)
KL-6 test category				< 0.001
1	355 (27.4)	295 (33.7)	60 (14.2)
2	647 (49.9)	578 (66.1)	69 (16.3)
3	283 (21.8)	0 (0.0)	283 (67.1)
Unknown	12 (0.9)	2 (0.2)	10 (2.4)
ILD type	864 (66.6)	670 (76.6)	194 (46.0)	< 0.001
DILD	59 (6.8)	9 (1.3)	50 (25.8)
RP	120 (13.9)	1 (0.2)	119 (61.3)
AE-ILD	685 (79.3)	660 (98.5)	25 (12.9)
Survival				0.001
Live	730 (56.3)	486 (55.5)	244 (57.8)
Death	172 (13.3)	99 (11.3)	73 (17.3)
Lost F/U or Hopeless discharge	395 (30.4)	290 (33.2)	105 (24.9)
Values are presented as medians (ranges) or numbers (%). LC, lung cancer; ILD, interstitial lung disease; COPD, chronic obstructive pulmonary disease; ECOG, Eastern Cooperative Oncology Group; PS, performance status; FEV1, forced expiratory volume within 1 second; FVC, forced vital capacity; DLCO, diffusing capacity of carbon monoxide; CEA, carcinoembryonic antigen; CRP, C-reactive protein; PCT, procalcitonin; ADC, adenocarcinoma; SQCC, squamous cell carcinoma; NSCLC, non-small cell lung carcinoma; NOS, not otherwise specified; SCLC, small cell lung carcinoma; LD, limited disease; ED, extensive disease; EGFR, epidermal growth factor receptor; ALK, anaplastic lymphoma kinase; ROS1, ROS proto-oncogene 1; PD-L1, programmed death-ligand 1; IHC, immunohistochemistry; TPS, tumor proportion score; CCRT, concurrent chemoradiation therapy; SBRT, stereotactic body radiation therapy; RT, radiation therapy; IrAE, immune-related adverse event; DILD, drug-induced ILD; RP, radiation-induced pneumonitis; AE-ILD, acute exacerbation of ILD; F/U, follow-up.

Overall, the median serum KL-6 level (U/mL) was higher among patients who developed ILD than among those without ILD (600.7 vs 326.7; p < 0.001) and higher among patients without lung cancer than among those with lung cancer (556.5 vs 369.3; p < 0.001) (Fig. 2a-b). However, in categories 1 and 2, there were no differences in serum KL-6 levels between patients with and without lung cancer (Fig. 2c).

Among lung cancer patients, the median serum KL-6 levels were significantly higher in categories 1 and 2, respectively, than in category 3 (492.2 vs 333.0; p = 0.019) (Fig. 3a), higher in patients with underlying ILD than in those without ILD (821.3 vs 335.8; p < 0.001) (Fig. 3b), and lower in patients with good ECOG PS scores than in those with poor PS scores (330.7 vs 506.8; p < 0.001) (Fig. 3c). Patients with adenocarcinoma had a higher median serum KL-6 level than those with squamous cell carcinoma (519.4 vs 317.8; p < 0.001) and small cell carcinoma (519.4 vs 322.4 ; p < 0.001) (Fig. 3d), and patients with advanced-stage disease had a higher median serum KL-6 level than those with early-stage lung cancer (409.1 vs 321.0; p = 0.007) (Fig. 3e). Additionally, serum KL-6 level had a negative correlation with FVC (L) (r=-0.11; p = 0.033) (Fig. 3f) and DLCO (%) (r=-0.11; p = 0.031) (Fig. 3g), as well as a positive correlation with CEA (r = 0.21; p < 0.001) (Fig. 3h) and C-reactive protein (r = 0.16, p = 0.006) (Fig. 3i).

Serum KL-6 and TR-ILD in lung cancer

There were 373 lung cancer patients treated with RT (n = 273) or ICIs (n = 276), and 194 patients developed TR-ILD (Table 1). The median serum KL-6 level was higher among patients with TR-ILD than among those without TR-ILD, although this difference was not significant. (394.4 vs 333.5; p = 0.079) (Fig. 4a). However, for categories 1 and 2, patients with TR-ILD had a significantly higher median serum KL-6 level than those without TR-ILD (531.0 vs 261.8; p = 0.045). In terms of the TR-ILD subtypes, the median serum KL-6 level was higher among patients with DILD than among those without ILD (575.9 vs 333.5; p = 0.004) or among those with RP (vs 330.7; p = 0.001). Patients with AE-ILD (937.1 U/mL) also had a higher median serum KL-6 level than those without ILD (p = 0.001) or those with RP (p < 0.001), although there was no significant difference compared with patients with DILD (Fig. 4b). Furthermore, the median serum KL-6 level correlated with the severity of TR-ILD (323.5 in grade 1 vs 561.1 in grades 2–4; p = 0.002) (Fig. 4c-d).

The cutoff serum KL-6 level for severe TR-ILD (grade 2 or higher) was determined by receiver operating characteristic curve analysis, and the optimal value was 449.9 U/mL, with a sensitivity of 64.6% and a specificity of 68.8% (area under the curve: 0.690, 95% CI: 0.614–0.767; p < 0.001).

Risk factors for developing severe TR-ILD

In the univariate analysis, underlying ILD, a high ECOG PS score (2–4), the presence of EGFR mutations, previous RT or ICI treatment within 90 days, the presence of immune-related adverse events, and a high serum KL-6 level (≥ 449.9 U/mL) were significant risk factors for severe TR-ILD among lung cancer patients (Fig. 5a). In the multivariate analysis, a high serum KL-6 level was an independent risk factor for severe TR-ILD (odds ratio: 2.76, 95% CI: 1.11–6.90; p = 0.029). Furthermore, in categories 1 and 2, a high serum KL-6 with a normal PCT level was associated with severe TR-ILD rather than non-ILD respiratory disease or non-severe TR-ILD (odds ratio: 5.93, 95% CI: 2.03–17.32; p = 0.001) (Fig. 5b).

Serum KL-6 levels and prognosis

Survival follow-up was started on the date of the first serum KL-6 measurement. On the data cutoff date (February 22, 2022), the median follow-up duration of lung cancer patients was 18.7 months (95% CI: 17.0-20.3). The events of death, hopeless discharge, or loss of follow-up occurred in 178 patients (42.2%) follow-up, and the median overall survival (OS) was 6.3 months (95% CI: 5.83–6.84).

The median OS was significantly shorter among patients with high serum KL-6 levels (≥449.9 U/mL; 7.1 months, 95% CI: 4.2–9.9) than among those with low serum KL-6 levels (< 449.9 U/mL; 16.4 months, 95% CI: 11.2–21.7), with an HR of 1.78 (95% CI: 1.33–2.39; p < 0.001) (Fig. 5c). In category 3 of lung cancer patients, the events of interest occurred in 108 patients (38.2%), and the OS trend of category 3 patients was similar to the overall trend of all the lung cancer patients. The median OS was significantly shorter among patients with high serum KL-6 levels (8.1 months, 95% CI: 5.1–11.1) than among those with low serum KL-6 levels (16.4 months, 95% CI: 10.8–22.0), with an HR of 1.90 (95% CI: 1.30–2.78; p = 0.001) (Fig. 5d).

A representative case of longitudinal monitoring with serum KL-6 is shown in Fig. 5e. A 75-year-old man with stage-IIIC (T3N3M0) squamous cell carcinoma of the right lower lobe and mediastinal lymph nodes (red arrows) received—as a consolidation treatment—durvalumab, an anti-PD-L1 ICI, after the completion of CCRT (without progression). He had grade-2 exertional dyspnea on the mMRC (modified Medical Research Council) scale¹⁴ 2 weeks after starting durvalumab, and an area of consolidation was revealed in the right lung on his chest X-ray (red circle), which was concordant with a slight increase in his serum KL-6 level (405 U/mL), suggesting pneumonitis. During a month-long cessation of durvalumab, repeat X-ray examination revealed improvement of the consolidation (dashed red circle, coinciding with an improvement in his symptoms), and his serum KL-6 level decreased to 216 U/mL. After the resumption of the durvalumab treatment, his respiratory symptoms (grade-3 dyspnea on the mMRC scale) and X-ray features of ground-glass opacities mixed with consolidation (in both lung fields) were aggravated (blue circle and blue arrows), and his serum KL-6 level markedly increased to 1012 U/mL, reflecting a recurrence of pneumonitis. His respiratory symptoms and imaging findings (dashed blue circle and arrows) resolved after the durvalumab was withdrawn and steroid treatment was initiated, and his serum KL-6 level gradually declined (678 U/mL). However, distant metastases (brain; yellow arrows) were detected during his restaging workup (likely due to the interruption of treatment), and he underwent subsequent systemic chemotherapy.

This retrospective cohort study included patients with and without lung cancer who underwent serum KL-6 testing, which was conducted when an ILD event was suspected or before lung cancer treatment started. We investigated the usefulness of serum KL-6 in the diagnosis and severity assessment of TR-ILD, as well as in the prediction of TR-ILD development and survival in lung cancer patients. A high serum KL-6 level was an independent risk factor for severe TR-ILD, and a high serum KL-6 with a normal PCT level was associated with severe TR-ILD rather than non-ILD respiratory disease or non-severe TR-ILD. Furthermore, patients with high serum KL-6 levels had worse OS than those with low serum KL-6 levels, regardless of the timing of the test. This study demonstrated that serum KL-6 could be a biomarker for the diagnosis, management, and prognostication of TR-ILD in lung cancer patients.

KL-6 has been used and validated as a potential biomarker for diagnosing and indicating the severity and progression of ILD, especially in idiopathic interstitial pneumonias, including idiopathic pulmonary fibrosis (IPF) ^15–18. In several meta-analyses, elevated serum KL-6 has been associated with disease activity, severity, and survival in the context of ILD ^12,19; continuously increasing serum KL-6 has been demonstrated as an indicator of poor clinical outcomes ¹². Particularly, in patients with connective tissue disease, serum KL-6 level has been shown to be higher in patients with ILD than in those without ILD, with serum KL-6 level being negatively correlated with lung function (FVC and DLCO) and positively with the extent of ILD ¹³. In the present study, the median serum KL-6 level was a useful biomarker in diagnosing ILD, and it was significantly higher in patients who developed ILD than in those without ILD. Most patients without lung cancer developed ILD as an acute exacerbation of underlying idiopathic ILD, including IPF, non-specific interstitial pneumonitis (NSIP), cryptogenic organizing pneumonia (COP), and connective tissue disease–associated ILD. Most of the serum KL-6 levels in patients without lung cancer were measured when respiratory symptoms deteriorated and ILD or non-ILD respiratory disease was suspected. However, this study was not designed to collect data on baseline KL-6 levels at the time of diagnosis of those with idiopathic ILD, and we did not focus on the validation of serum KL-6 as a predictive and prognostic biomarker of idiopathic ILD in patients without lung cancer.

In contrast to idiopathic ILD, the value of serum KL-6 for predicting the development of ILD has not been verified in lung cancer patients. In a retrospective Japanese study ²⁰, the proportion of patients with high serum KL-6 levels (> 500 U/mL) was higher among lung cancer patients with ILD (73.5%) than among those without ILD (33.7%). In a systematic review and meta-analysis, higher levels of KL-6 at baseline were associated with AE-ILD following lung cancer resection ²¹. However, in the reports of these studies, the exact time point (baseline or onset) and reason for measuring serum KL-6 are not described ²⁰, or the causes or subtypes of ILD are not defined ²¹. In the present study, we divided patients into three subgroups according to the timing and purpose of serum KL-6 testing in order to verify the significance of serum KL-6 in the diagnosis and severity assessment of ILD at onset (categories 1 and 2) and in predicting the occurrence of ILD before lung cancer treatment at baseline (category 3). Furthermore, ILD development was defined as a treatment-related event (TR-ILD), and the subtypes of ILD were categorized as DILD, RP, and AE-ILD, according to the cause of TR-ILD. The present study showed the same trend as previous studies of ILD in patients without lung cancer. A high serum KL-6 level (≥ 449.9 U/mL) was an independent predictor of the development of severe TR-ILD, and a high serum KL-6 level with a normal serum PCT level was associated with severe TR-ILD. Additionally, the median serum KL-6 level was significantly higher in the DILD and AE-ILD subgroups than in the RP or non-ILD subgroups. These results demonstrated that serum KL-6 could be useful as a predictive biomarker for differentiating between severe TR-ILD and non-severe TR-ILD or non-ILD respiratory disease and for assessing the severity of TR-ILD in lung cancer patients under treatment.

Serum KL-6 has been reported to be associated with the development and clinical course of DILD and RP. In several previous studies, elevated KL-6 has been observed in the majority of DILD patients ²², and serum KL-6 has been shown to change over time in response to treatment ^22,23. In patients with RP, post-RT serum KL-6 levels have been shown to increase relative to the pretreatment levels during or after thoracic RT ^24,25. However, in terms of the discrimination between subtypes of TR-ILD, caution needs to be exercised with respect to the positive predictive value of the KL-6 assay, as elevated serum KL-6 levels can vary according to radiologic patterns, as well as by the extent and severity of ILD. In the aforementioned studies, serum KL-6 levels were increased in DILD patients with diffuse alveolar damage, chronic interstitial pneumonia, or acute interstitial pneumonia patterns but not in those with bronchiolitis obliterans organizing pneumonia, eosinophilic pneumonia, or hypersensitivity pneumonitis patterns ^22,23. Additionally, serum KL-6 levels increased from baseline in patients with severe RP, while there was no significant change in patients with localized RP ²⁴. In the present study, the median serum KL-6 levels were significantly higher in the DILD and AE-ILD subgroups than in the RP or non-ILD subgroups, while patients with RP were not any different from those with non-ILD lung cancer in this regard. RP can be categorized as a localized subtype of TR-ILD compared with DILD or AE-ILD. Thus, taken together with the imaging findings, temporal causality, and the level of serum KL-6 in the case presentation (Fig. 5e), the first event of pneumonitis associated with a slight increase in serum KL-6 should be assumed to be RP. An increase in serum KL-6 levels can be correlated with increased regeneration of alveolar type II pneumocytes and enhanced permeability following the destruction of the air-blood barrier ^10,11,26. Therefore, the results of the present study are consistent with previous studies, suggesting that they can be steadily translated into real-world clinical practice.

Few studies have investigated KL-6 as a prognostic tumor marker in lung cancer patients. In a surgical cohort study, immunohistochemical findings in NSCLC correlated with serum KL-6 levels, and a high serum KL-6 level was associated with a poor prognosis in NSCLC patients who had undergone curative surgery ²⁷. In a retrospective Japanese study, elevated serum KL-6 was not associated with prognosis in lung cancer patients with ILD; however, it was one of the unfavorable prognostic factors in individuals without ILD ²⁰. In the present study, serum KL-6 levels were associated with the baseline characteristics of lung cancer, including comorbidity (underlying ILD), ECOG PS score, histology, stage (advanced), baseline lung function (FVC, DLCO), and a tumor marker (CEA). Furthermore, high serum KL-6 before cancer treatment was associated with shorter OS. The value of baseline serum KL-6 for predicting the development of TR-ILD was diluted in category 3, probably due to variations in comorbidities, stage, and histology in this group of patients. However, at the onset of TR-ILD, serum KL-6 level was a significant predictor in categories 1 and 2. Therefore, serum KL-6 before treatment and at the onset of TR-ILD could be used as a prognostic biomarker for lung cancer patients.

There were several limitations to the present study. First, as the clinical data of patients with and without lung cancer were collected retrospectively, there were imbalances between the groups, for example, in terms of comorbidities, PS, pulmonary function, the reason for KL-6 testing, and ILD subtypes (Table 1). However, the baseline comparison between the groups was not the primary outcome of the study, and we decided that matching patients between the groups according to the baseline characteristics was unnecessary, with consideration that the causes of ILD in the main population were lung cancer treatments. Second, there were insufficient instances of repeated tests and serial follow-up of serum KL-6 levels. Although we provided potential evidence of successful monitoring of serum KL-6 levels with a representative case (Fig. 5e), it was impossible to objectively demonstrate the utility of serum KL-6 monitoring with the small sample size, as the progress of ILD changed. In an ILD cohort study ²⁸, serial blood samples were collected from IPF patients with or without lung cancer before the initiation of antifibrotic therapy (nintedanib) and after 12 to 24 months. In this study, baseline serum KL-6 levels were higher in IPF patients with lung cancer than in those without lung cancer, and an elevation in serum KL-6 was correlated with a significant decline in FVC during follow-up. A large prospective cohort study that includes specific lung cancer populations stratified by stage, histology, treatment modality, or the timing of repeat KL-6 testing is needed in the near future.

In conclusion, the present study demonstrated that a high serum KL-6 level at the onset of an ILD event was an independent predictor of the development of severe TR-ILD, and a combination of serum KL-6 and PCT levels was useful for distinguishing severe TR-ILD from non-severe TR-ILD or non-ILD respiratory disease. The serum KL-6 level was associated with several baseline characteristics of lung cancer and causality-related subtypes of TR-ILD. Furthermore, a high serum KL-6 level before treatment and at the onset of TR-ILD was a significant and negative prognostic factor in terms of survival in lung cancer patients. These findings could provide valuable insights into clinical vigilance and management of TR-ILD with timely serum KL-6 testing during lung cancer treatment. Future larger-scale prospective studies are warranted to validate the clinical significance and prognostic potential of serum KL-6 for lung cancer patients who undergo treatment that might cause ILD.

Patients and assessment of ILD

We recruited patients with or without lung cancer who were tested for serum KL-6 at Chonnam National University Hwasun Hospital between January 2020 and January 2022. We divided study patients into three groups based on the reason for KL-6 measurement: for differentiating between pneumonia and ILD (category 1), diagnosing and assessing the severity of suspicious ILD (category 2), and evaluating the baseline level before initiating cancer treatment such as radiation therapy (RT) or ICI administration (category 3). Computed tomographic images were evaluated for the presence of ILD at the time of the event or before the treatment of lung cancer. To confirm a diagnosis as ILD, two experts in radiology and pulmonology checked the images. TR-ILD was diagnosed clinically based on the presence of classic symptoms of ILD, the onset time of symptoms, a history of lung cancer treatment, imaging findings, and exclusion of alternative causes. ILD was categorized as follows: drug-induced ILD (DILD), radiation-induced pneumonitis (RP), or acute exacerbation of underlying ILD (AE-ILD).

Data collection

We conducted a retrospective cohort study using a clinical database and lung cancer registry of Chonnam National University Hwasun Hospital, with data collected by pulmonology specialists. The database contains information on personal details (e.g., patient identifiers, date of birth, and sex), medical history (e.g., family and personal history of cancer, smoking status, comorbidities), lung cancer characteristics (e.g., stage at registry enrollment, Eastern Cooperative Oncology Group [ECOG] performance status [PS]), pulmonary comorbidities, pulmonary function, EGFR mutation, anaplastic lymphoma kinase (ALK) rearrangement, and PD-L1 tumor proportional score. ECOG PS score was categorized as good (0 to 1) or poor (2 to 4). Additionally, longitudinal information on the treatment of lung cancer and ILD was available in the database and registry through institutional electronic health records, which allowed this study to capture the type, dose, and date of administration of treatment at the patient level. At the time of analysis after data collection, all patient information was anonymized. Data on pulmonary function, inflammatory markers (such as C-reactive protein and procalcitonin [PCT]), and tumor markers (such as carcinoembryonic antigen [CEA]) were based on the results of tests performed around the time point of the serum KL-6 measurements. The variables reflecting pulmonary function were forced expiratory volume within 1 second (FEV1), forced vital capacity (FVC), and diffusing capacity of lung for carbon monoxide (DLCO). In patients who were confirmed to have developed ILD, we assessed the severity of TR-ILD according to the Common Terminology Criteria for Adverse Events (version 5.0), and we defined the severe TR-ILD as grade 2 or higher.

The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013) and Good Clinical Practice guidelines. This study was approved by the Institutional Review Board of the Chonnam National University Hwasun Hospital (CNUHH-2022-206). The requirement for patient consent was waived by the Institutional Review Board of the Chonnam National University Hwasun Hospital because of the retrospective nature of the study and because the analysis used anonymized clinical data.

Blood sample collection and measurement of serum KL-6 levels

Serum KL-6 levels (U/mL) were measured using an AU 5800 chemistry analyzer (Beckman Coulter, Brea, CA, USA) with the Nanopia KL-6 assay (Sekisui Medical Co., Ltd., Tokyo, Japan). Serum KL-6 tests might have been repeated, and the results were monitored by attending physicians according to the clinical course of TR-ILD.

Statistical analysis

To compare serum KL-6 levels between subgroups, we used the t-test and one-way ANOVA (analysis of variance) followed by Tukey’s post hoc test. Pearson’s correlation coefficient was used to analyze the associations between serum KL-6 levels and several covariates, such as pulmonary function, tumor markers, and inflammatory markers. Receiver operating characteristic curve analysis was performed to demonstrate the optimal serum KL-6 cutoff value for predicting severe TR-ILD. Chi-square and logistic regression analyses were performed to determine risk factors for severe TR-ILD. Survival times were measured from the respective dates when serum KL-6 levels were measured for the first time, and these were estimated for serum KL-6–based subgroups using the Kaplan-Meier method. Univariate and multivariate analyses of survival were performed using Cox proportional hazards modeling. Statistical analysis was performed using SPSS Statistics for Windows, version 27 (IBM Corp., Armonk, NY, USA) and R version 4.2.3 (R Foundation for Statistical Computing, Vienna, Austria) ²⁹. A p-value less than 0.05 was considered statistically significant.

Acknowledgments

This research was supported by a National Research Foundation of Korea grant funded by the Korean government (NRF-2019M3E5D1A02067951 to C. K. Park). The funder had no role in the study design, data collection, analysis, decision to publish, or preparation of the manuscript. This study was presented at the Korean Academy of Tuberculosis and Respiratory Disease International Conference 2021, held in Seoul, Republic of Korea (November 11-12, 2021).

Data Availability

The data presented in this study are available on request from the corresponding author. The data are not publicly available due to institutional data-sharing restrictions.

Additional Information

The authors declare no competing interest.

Author Contributions

Hwa Kyung Park(HKP), Chang-Seok Yoon(CSY), Young-Ok Na(YON), Jae-Kyeong Lee(JKL), Hyung-Joo Oh(HJO), Ha-Young Park(HYP), Bo-Gun Kho(BGK), Tae-Ok Kim(TOK), Hong-Joon Shin(HJS), Yong-Soo Kwon(YSK), In-Jae Oh(IJO), Yu-Il Kim(YIK), Sung-Chul Lim(SCL), Young-Chul Kim(YCK), Cheol-Kyu Park(CKP)

Conceptualization: CKP

Data curation: HKP, CKP

Formal analysis: HKP, CKP

Funding acquisition: CKP

Investigation: all authors

Methodology: HKP, CKP

Project administration: CKP

Resources: all authors

Software: HKP, CKP

Supervision: all authors

Validation: all authors

Visualization: HKP, CKP

Writing – original draft: HKP, CKP

Writing – review and editing: all authors

Sung, H. et al. Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA Cancer J Clin 71, 209-249, doi:https://doi.org/10.3322/caac.21660 (2021).
Hong, S. et al. Cancer Statistics in Korea: Incidence, Mortality, Survival, and Prevalence in 2018. Cancer Res Treat 53, 301-315, doi:10.4143/crt.2021.291 (2021).
Chang, C. H. & Chang, Y. C. Comparing the Therapeutic Efficacies of Lung Cancer: Network Meta-Analysis Approaches. Int J Environ Res Public Health 19, doi:10.3390/ijerph192114324 (2022).
Wu, Y.-L. et al. Osimertinib in Resected EGFR-Mutated Non–Small-Cell Lung Cancer. N Engl J Med 383, 1711-1723, doi:10.1056/NEJMoa2027071 (2020).
Forde, P. M. et al. Neoadjuvant Nivolumab plus Chemotherapy in Resectable Lung Cancer. N Engl J Med 386, 1973-1985, doi:10.1056/NEJMoa2202170 (2022).
Felip, E. et al. Adjuvant atezolizumab after adjuvant chemotherapy in resected stage IB-IIIA non-small-cell lung cancer (IMpower010): a randomised, multicentre, open-label, phase 3 trial. Lancet 398, 1344-1357, doi:10.1016/s0140-6736(21)02098-5 (2021).
O'Brien, M. et al. Pembrolizumab versus placebo as adjuvant therapy for completely resected stage IB-IIIA non-small-cell lung cancer (PEARLS/KEYNOTE-091): an interim analysis of a randomised, triple-blind, phase 3 trial. Lancet Oncol 23, 1274-1286, doi:10.1016/s1470-2045(22)00518-6 (2022).
Spigel, D. R. et al. Five-Year Survival Outcomes From the PACIFIC Trial: Durvalumab After Chemoradiotherapy in Stage III Non-Small-Cell Lung Cancer. J Clin Oncol 40, 1301-1311, doi:10.1200/jco.21.01308 (2022).
Saito, G. et al. Real-world survey of pneumonitis and its impact on durvalumab consolidation therapy in patients with non-small cell lung cancer who received chemoradiotherapy after durvalumab approval (HOPE-005/CRIMSON). Lung Cancer 161, 86-93, doi:10.1016/j.lungcan.2021.08.019 (2021).
Kohno, N. et al. KL-6, a mucin-like glycoprotein, in bronchoalveolar lavage fluid from patients with interstitial lung disease. Am Rev Respir Dis 148, 637-642, doi:10.1164/ajrccm/148.3.637 (1993).
Ishikawa, N., Hattori, N., Yokoyama, A. & Kohno, N. Utility of KL-6/MUC1 in the clinical management of interstitial lung diseases. Respir Investig 50, 3-13, doi:10.1016/j.resinv.2012.02.001 (2012).
Zhang, T., Shen, P., Duan, C. & Gao, L. KL-6 as an Immunological Biomarker Predicts the Severity, Progression, Acute Exacerbation, and Poor Outcomes of Interstitial Lung Disease: A Systematic Review and Meta-Analysis. Front Immunol 12, doi:10.3389/fimmu.2021.745233 (2021).
Lee, J. S. et al. Serum KL-6 levels reflect the severity of interstitial lung disease associated with connective tissue disease. Arthritis Res Ther 21, 58, doi:10.1186/s13075-019-1835-9 (2019).
Mahler, D. A. & Wells, C. K. Evaluation of clinical methods for rating dyspnea. Chest 93, 580-586, doi:10.1378/chest.93.3.580 (1988).
Zheng, P. et al. Diagnostic value of KL-6 in idiopathic interstitial pneumonia. J Thorac Dis 10, 4724-4732, doi:10.21037/jtd.2018.07.54 (2018).
Yokoyama, A. et al. Prognostic value of circulating KL-6 in idiopathic pulmonary fibrosis. Respirology 11, 164-168, doi:10.1111/j.1440-1843.2006.00834.x (2006).
Bergantini, L. et al. Utility of serological biomarker' panels for diagnostic accuracy of interstitial lung diseases. Immunol Res 68, 414-421, doi:10.1007/s12026-020-09158-0 (2020).
Wakamatsu, K. et al. Prognostic value of serial serum KL-6 measurements in patients with idiopathic pulmonary fibrosis. Respir Investig 55, 16-23, doi:10.1016/j.resinv.2016.09.003 (2017).
Zhang, H. et al. Diagnostic and prognostic predictive values of circulating KL-6 for interstitial lung disease: A PRISMA-compliant systematic review and meta-analysis. Medicine (Baltimore) 99, e19493, doi:10.1097/md.0000000000019493 (2020).
Miyazaki, K. et al. Serum KL-6 levels in lung cancer patients with or without interstitial lung disease. J Clin Lab Anal 24, 295-299, doi:10.1002/jcla.20404 (2010).
Hao, X. et al. Risk factors for acute exacerbation of interstitial lung disease following lung cancer resection: a systematic review and meta-analysis. Interact Cardiovasc Thorac Surg 34, 744-752, doi:10.1093/icvts/ivab350 (2022).
Ohnishi, H. et al. Circulating KL-6 levels in patients with drug induced pneumonitis. Thorax 58, 872-875, doi:10.1136/thorax.58.10.872 (2003).
Kawase, S. et al. Change in serum KL-6 level from baseline is useful for predicting life-threatening EGFR-TKIs induced interstitial lung disease. Respir Res 12, 97, doi:10.1186/1465-9921-12-97 (2011).
Goto, K. et al. Serum levels of KL-6 are useful biomarkers for severe radiation pneumonitis. Lung Cancer 34, 141-148, doi:10.1016/s0169-5002(01)00215-x (2001).
Hara, R., Itami, J., Komiyama, T., Katoh, D. & Kondo, T. Serum levels of KL-6 for predicting the occurrence of radiation pneumonitis after stereotactic radiotherapy for lung tumors. Chest 125, 340-344, doi:10.1378/chest.125.1.340 (2004).
Ohnishi, H. et al. Comparative study of KL-6, surfactant protein-A, surfactant protein-D, and monocyte chemoattractant protein-1 as serum markers for interstitial lung diseases. Am J Respir Crit Care Med 165, 378-381, doi:10.1164/ajrccm.165.3.2107134 (2002).
Tanaka, S. et al. Krebs von den Lungen-6 (KL-6) is a prognostic biomarker in patients with surgically resected nonsmall cell lung cancer. Int J Cancer 130, 377-387, doi:https://doi.org/10.1002/ijc.26007 (2012).
d'Alessandro, M. et al. Serum Concentrations of KL-6 in Patients with IPF and Lung Cancer and Serial Measurements of KL-6 in IPF Patients Treated with Antifibrotic Therapy. Cancers (Basel) 13, doi:10.3390/cancers13040689 (2021).
RC, T. A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria (2021).

No competing interests reported.

Download PDF

Journal Publication

published 23 Oct, 2023

Read the published version in Scientific Reports →

Editorial decision: Major revision
25 Aug, 2023
Reviews received at journal
16 Aug, 2023
Reviewers agreed at journal
07 Aug, 2023
Reviewers invited by journal
21 Jul, 2023
Editor assigned by journal
21 Jul, 2023
Editor invited by journal
07 May, 2023
Submission checks completed at journal
07 May, 2023
First submitted to journal
02 May, 2023

You are reading this latest preprint version

Serum KL-6 levels predict the occurrence and severity of treatment-related interstitial lung disease in lung cancer

Status:

Journal Publication

Version 1

Abstract

Figures

Introduction

Results

Baseline characteristics and serum KL-6 levels

Serum KL-6 and TR-ILD in lung cancer

Risk factors for developing severe TR-ILD

Serum KL-6 levels and prognosis

Discussion

Methods

Patients and assessment of ILD

Data collection

Blood sample collection and measurement of serum KL-6 levels

Statistical analysis

Declarations

References

Additional Declarations

Status:

Journal Publication

Version 1