Association Between Immune-Related Hypothyroidism and Survival Outcomes in Patients with Head and Neck Cancer Treated with Nivolumab

Immune-related hypothyroidism (irHT) triggered by nivolumab is known to affect drug ecacy in patients with non-small cell lung cancer (NSCLC). However, it is unclear whether there is an association between the drug ecacy and nivolumab-induced irHT in recurrent and/or metastatic head and neck cancer (R/M HNC). Hence, we retrospectively investigated the relationship between irHT and treatment outcomes in R/M HNC patients treated with nivolumab.


Abstract
Background Immune-related hypothyroidism (irHT) triggered by nivolumab is known to affect drug e cacy in patients with non-small cell lung cancer (NSCLC). However, it is unclear whether there is an association between the drug e cacy and nivolumab-induced irHT in recurrent and/or metastatic head and neck cancer (R/M HNC). Hence, we retrospectively investigated the relationship between irHT and treatment outcomes in R/M HNC patients treated with nivolumab.

Methods
Patients with R/M HNC who received nivolumab monotherapy between April 2017 and June 2019 were selected. Those receiving levothyroxine treatment and with thyroid-stimulating hormone (TSH) levels > 10 µIU/mL before nivolumab administration were excluded. irHT was de ned as one measurement of free T4 (FT4) < 0.8 ng/dL and/or TSH > 10 µIU/mL or as two successive abnormal levels of FT4 and/or TSH after nivolumab administration. To assess therapeutic e cacy, nivolumab-treated patients were divided into two groups: with or without irHT [irHT (+) and irHT (−) groups, respectively].

Conclusions
Our results suggest that the development of irHT, similarly to NSCLC, is associated with improved survival outcomes in R/M HNC patients treated with nivolumab.

Background
Combination chemotherapy with cisplatin, 5-uorouracil, and cetuximab has been recommended for patients with recurrent and/or metastatic head and neck cancer (R/M HNC) [1]. Patients with R/M HNC exhibiting disease progression within 6 months of initiation of platinum combination chemotherapy have poor prognoses, and researchers have only recently identi ed agents that can improve the survival rates [2] [3]. Nivolumab is an anti-programmed cell death-1 (PD-1) antibody that has been established as a more effective agent than standard chemotherapy for treating patients with platinum-refractory R/M HNC [4][5][6]. PD-1 ligands, PD-L1 and PD-L2, expressed on cancer-cell surfaces bind to PD-1 receptors on cytotoxic T-cells to inhibit their activation. The anti-tumor effect of nivolumab results from selectively binding to PD-1 receptors, thus blocking the inhibitory interaction of cancer cells with cytotoxic T-cells, leading to activation of the latter.
Despite the clinical bene ts of nivolumab treatment, activation of host immunity by the drug causes overreactions from normal cells or immune-related adverse events (irAEs). These irAEs affect organs such as the skin, gastrointestinal tract, liver, and endocrine system [7]. The occurrence of irAEs may re ect both side effects and anti-tumor responses because of the anti-PD-1 treatment. A previous study in patients with non-small cell lung cancer (NSCLC) suggested that anti-PD-1-triggered irAE is often associated with the prolonged survival [8]. Interestingly, thyroid dysfunction is associated with prolonged overall survival (OS) in NSCLC patients treated with anti-PD-1 agents [9] [10].
Hypothyroidism is one of the most common irAEs, with up to 10% incidence in nivolumab-treated patients [11] [12]. However, limited information is available on the relationship between immune-related hypothyroidism (irHT) and therapeutic e cacy in patients with R/M HNC treated with nivolumab. Therefore, this study aimed to analyze the impact of irHT onset on therapeutic e cacy in patients with R/M HNC treated with nivolumab.

Study design, setting, and patient population
We retrospectively assessed nivolumab e cacy and toxicity in patients with R/M HNC from April 2017 to June 2019 at Kyushu University Hospital. The present study was approved by the Ethics Committee of the Kyushu University Hospital (Approval No. 2020 − 155) and was conducted in accordance with the principles of the Helsinki Declaration. The subjects comprised patients who received either 3 mg/kg or 240 mg of nivolumab per person every 2 weeks. Nivolumab was administered until disease progression or unacceptable toxicity was con rmed. Clinical data were extracted from electronic medical records: age, sex, Eastern Cooperative Oncology Group performance status, number of previous chemotherapies, most common metastatic sites, lines of chemotherapy after nivolumab treatment, and course of nivolumab treatment.

Evaluation of irHT and therapeutic effects
The clinical severity of irAEs, including irHT, was graded using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. The best overall response rate was determined in accordance with Response Evaluation Criteria in Solid Tumors version 1.1. The time for treatment assessment was determined by each physician. OS was de ned as the time from the start of nivolumab treatment to the patient's death. Progression-free survival (PFS) was de ned as the time from the start of nivolumab treatment to disease progression or death. The disease control rate (DCR) was de ned as complete or partial response or stable disease, based on the evaluation of clinical response by computed tomography. The primary endpoint of this study was the determination of the relationship between irHT onset and OS in patients with R/M HNC. As secondary endpoints, we assessed the relationships between irHT onset and PFS or DCR and between irHT onset and other irAEs.

Statistical analysis
Categorical variables were analyzed using Chi-square or Fisher's exact test, whereas continuous variables were analyzed using the Mann-Whitney U-test. The Kaplan-Meier method with log-rank tests was used to assess OS and PFS. The follow-up period was at least 6 months from the start of nivolumab treatment.
Data collection of patients without disease progression or unacceptable toxicity was completed at the end of June 2019. Data were analyzed using JMP 14.0.0 (SAS Institute Inc., Cary, NC, USA) and GraphPad PRISM version 8 (GraphPad Software, San Diego, CA, USA); p < 0.05 was considered to indicate a statistically signi cant difference between two groups.

Patient characteristics
The study included 62 patients with R/M HNC who received nivolumab. We excluded 19 patients with preexisting hypothyroidism, 17 on concomitant treatment with levothyroxine, and 2 with TSH ≥ 10 µIU/mL before nivolumab administration. We also excluded 6 patients whose treatments were discontinued within 28 days due to death, disease progression, or appearance of intolerable irAEs. Another 6 patients were excluded because they were transferred to other hospitals. Thus, the nal analysis involved 31 patients ( Fig. 1), 14 of whom (45%) showed some form of irHT. The number of nivolumab treatment courses in patients with irHT (median = 14 courses, range 4 − 39) was signi cantly higher than that in patients without irHT (median = 7 courses, range 4 − 25). Baseline TSH levels in irHT(+) and irHT(−) groups were 4.71 µIU/mL (range, 1.13-9.18 µIU/mL) and 1.82 µIU/mL (range, 0.85-4.02 µIU/mL), respectively. The baseline TSH level in the irHT(+) group was signi cantly higher than that in the irHT(−) group (p < 0.001). Baseline FT4 levels in irHT(+) and irHT(−) groups were 1.10 ng/dL (range, 0.90-1.64 ng/dL) and 1.25 ng/dL (range, 1.01-1.68 ng/dL), respectively. The baseline FT4 level in the irHT(+) group was signi cantly lower than that in the irHT(−) group ( p = 0.0252). The two groups did not differ in age, sex, performance status, number of previous chemotherapies, most common metastatic sites, or postnivolumab lines of chemotherapy (Table 1). Time to irHT onset In the irHT (+) group, the median duration from the start of nivolumab treatment to irHT onset was 76 days (range 17-274 days) (Fig. 2). The incidence of irHT severity was 50.0% (n = 7) at grade 1 and 50.0% (n = 7) at grade 2. Seven patients at grade 2 began treatment with levothyroxine that continued throughout the observation period. irHT was found to occur in 5 patients with two successive measurements of FT4 < 1.0 ng/dL, 4 patients with two successive measurements of TSH > 4.2 µIU/mL, 3 patients with TSH > 10 µIU/mL, and 2 patients with two successive measurements of TSH > 4.2 µIU/mL and FT4 < 1.0 ng/dL, respectively.

Discussion
In this study, OS and PFS for nivolumab treatment were signi cantly prolonged in the irHT (+) group of patients with R/M HNC. The DCR was signi cantly higher in the irHT (±) group than in the irHT (−) group. These results suggest that irHT by nivolumab treatment is involved in clinical bene t in patients with R/M HNC.
The occurrence of irAEs is more frequent in organs such as the skin, gastrointestinal tract, liver, and endocrine system [7]. Endocrine dysfunction includes thyroid dysfunction, hypopituitarism, hypoadrenocorticism, hypoparathyroidism, and type 1 diabetes [13]. Furthermore, thyroid dysfunction is classi ed into two types, hyperthyroidism and hypothyroidism. In particular, hypothyroidism is a common irAE caused by nivolumab treatment, and the incidence of nivolumab-induced irHT is 10% in melanoma [14], 15% in NSCLC [15], and 7.6% in R/M HNC [4]. Interestingly, 45% (14/31) of patients with R/M HNC in this study experienced irHT with nivolumab treatment. Although irAEs are typically evaluated using CTCAE, we evaluated irHT in this study based on our hospital's criteria. Symptoms of thyroid dysfunction are often absent or vague. Therefore, routine surveillance of thyroid function at each visit is necessary to identify these disorders. In fact, if hormone levels are low, hormone-replacement therapy is recommended (if TSH < 0.5 times the lower limit of normal, > 2 times the upper limit of normal, or consistently out of range in 2 subsequent measurements) [16 -20]. As the evaluation method using CTCAE does not use quanti ed objective data such as TSH, FT4, and FT3 levels, such an assessment of thyroid dysfunction may be an underestimation. For these reasons, the evaluation of thyroid dysfunction based on our hospital's criteria was considered to be more clinical in practice. Several studies have similarly assessed irHT based on their criteria, not on CTCAE, and reported the association between the onset of irHT and the clinical effect of nivolumab treatment [21]. Therefore, the high incidence of irHT in this study was attributed to the differences in evaluation methods.
It is di cult to predict the onset of irAE. However, Weber et al. [22] reported that the median time to onset of nivolumab-induced endocrine dysfunction was 73 days in melanoma. Nivolumab-induced hypothyroidism is considered to occur after a transient and asymptomatic period of hyperthyroidism [9]. Moreover, the median onset of hypothyroidism was 98 days in NSCLC [9]. Our results are supported by these results because the median onset of irHT was 76 days in this study. Seven patients (50.0%) classi ed as grade 2 in the irHT (+) group required treatment with levothyroxine during the observation period. In general, irHT has been reported as an irreversible adverse event [23]. These results suggest that it is important to constantly monitor the TSH and FT4 levels during the treatment period, especially in the rst 3 months of treatment with nivolumab.
The relationship between the onset of irAEs and the clinical bene ts of nivolumab is evaluated based on the anti-tumor effects of nivolumab on T cells to regulate and reactivate the immune response to tumor cells. However, irAEs are attributed to excessive autoimmune effects associated with the activation of normal cells. Several studies have reported an association of the onset of irAEs with clinical bene ts in the treatment with immune checkpoint inhibitors (ICIs) [8] [24][25][26]. Freedman et al. [24] reported that cutaneous irAEs increased the prolongation of OS in melanoma. Moreover, Ricciuti et al. [25] reported that gastrointestinal tract and endocrine irAEs increased clinical bene ts such as prolongation of the OS in NSCLC. In this study, clinical outcomes, such as OS and PFS, were signi cantly prolonged in the nivolumab-induced irHT (+) group. We also found that the DCR was signi cantly higher in the irHT (+) group than in the irHT (-) group. This result suggests that suppression of tumor growth might contribute to the prolongation of OS and PFS in the irHT (+) group.
In general, except for the onset of severe irAEs, such as interstitial pneumonia, renal dysfunction, and myasthenia gravis, ICI treatment can be continued with careful management of irAEs. The incidence of multiple irAEs was signi cantly higher in the irHT (+) group than in the irHT (-) group. DCR was also signi cantly higher in the irHT (+) group than in the irHT (-) group. Weber et al. [22] supported our results by reporting that patients with advanced melanoma who achieved an objective response to treatment with nivolumab experienced multiple irAEs. In this study, the number of nivolumab courses was signi cantly higher in the irHT (+) group than in the irHT (-) group. We speculated that the higher incidence of multiple irAEs in the irHT (+) group was related to more courses of nivolumab treatment and longer survival. However, since the frequency of serious irAEs did not differ between the irHT (+) and irHT (-) groups, appropriate treatment of irAEs by careful management may facilitate the continuation of nivolumab treatment in patients with R/M HNC.
Our study had several limitations. First, we excluded patients with hyperthyroidism or thyroiditis.
Therefore, we could not examine the relationship between irHT onset and clinical outcomes in these patients. Second, this analysis has lead-time bias. We showed that patients in the irHT (+) group after nivolumab treatment experienced better survival than those in the irHT (-) group. Although long-term survivors may have longer exposure to nivolumab and a higher risk of irHT onset, an extreme delay in the onset of irAEs is generally only observed in patients who respond to treatment [27]. Availability of data and materials The datasets used and analyzed during the current study are available from the corresponding authors on reasonable request. Figure 1 Patient enrollment owchart in this study. R/M HNC, recurrent and/or metastatic head and neck cancer; TSH, thyroid stimulating hormone; irHT, immune-related hypothyroidism.  Comparison of disease control rate between patients in the irHT (+) and irHT (-) groups; * p < 0.05.