Clinical Prediction Model for Necrosis of Nasal Septum Mucosal Flap After Salvage Surgery for Recurrent Nasopharyngeal Carcinoma

doi:10.21203/rs.3.rs-4725085/v1

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Clinical Prediction Model for Necrosis of Nasal Septum Mucosal Flap After Salvage Surgery for Recurrent Nasopharyngeal Carcinoma

https://doi.org/10.21203/rs.3.rs-4725085/v1

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Objective

To develop a predictive model assessing risk factors for nasal septal mucosal flap (NSF) necrosis in patients with recurrent nasopharyngeal carcinoma (NPC) undergoing endoscopic tumor resection and flap repair surgery.

Methods

A retrospective analysis was conducted on patients with recurrent NPC who underwent endoscopic salvage surgery and NSF repair. Factors analyzed included second-course radiotherapy history, recurrence T stage, recurrence time, and postoperative packing time. Logistic regression identified independent risk factors, and a predictive model was developed.

Results

Second-course radiotherapy, advanced T stage recurrence, longer recurrence time, and shorter postoperative packing time were identified as independent risk factors for NSF necrosis. Patients with second-course radiotherapy had an 8.338 times higher risk of flap necrosis. Advanced T stage and longer recurrence times were also associated with increased risk. Nasal packing for less than 5 days presented a higher risk of flap necrosis compared to packing for 5 days or more. The predictive model demonstrated good predictive ability.

Conclusion

The predictive model effectively identifies high-risk situations for NSF necrosis in recurrent NPC patients undergoing salvage surgery, aiding clinicians in precise surgical planning and targeted interventions to reduce complications, improve success rates, and enhance patient quality of life.

Recurrent nasopharyngeal carcinoma

Salvage surgery

nasalseptal flap

Flap necrosis

Nomogram

Clinical prediction model

Nasopharyngeal carcinoma (NPC) is a malignant tumor occurring in the nasopharynx, classified as a type of head and neck tumor. Radiotherapy is the preferred treatment for NPC, with approximately 90% of early-stage disease patients being curable through radiotherapy[1]. However, due to the concealed anatomical location and non-specific early symptoms, more than 70% of NPC patients are diagnosed at stage III or IV[2]. Approximately 20–30% of patients with advanced NPC are incurable due to recurrence and/or metastasis[3].

Treating recurrent NPC is challenging due to its complex anatomy and the effects of previous radiotherapy. Endoscopic surgery, as a minimally invasive technique, has been increasingly used to treat recurrent NPC. Postoperative wounds require the use of autologous tissue flaps, such as nasal septum mucosal flaps or temporal muscle flaps, for repair. Flap necrosis is a significant complication, impacting surgical outcomes, prolonging healing time, increasing infection risk, and necessitating further surgical interventions. This study aims to explore and identify risk factors for flap necrosis following endoscopic nasopharyngeal tumor resection and nasal septum mucosal flap repair in patients with recurrent NPC. By analyzing these factors, we hope to provide clinicians with information to optimize surgical strategies, reduce complications, and improve overall patient outcomes.

A retrospective analysis was conducted on 137 patients who underwent endoscopic nasopharyngeal tumor resection and nasal septum mucosal flap (or combined nasal floor mucosal flap) repair for recurrent NPC at Fujian Cancer Hospital from January 2017 to April 2024. Inclusion criteria: (1) diagnosed with recurrent NPC after admission; (2) initial treatment with standard radiotherapy; (3) received endoscopic nasopharyngeal tumor resection and nasal septum mucosal flap (or combined nasal floor mucosal flap) repair; (4) surgeries performed by the same surgical team at the institution. Exclusion criteria: preoperative systemic infectious diseases or incomplete clinical data. Collected variables included age, gender, preoperative history of second-course radiotherapy, preoperative EB virus levels, preoperative neutrophil-lymphocyte ratio, albumin, recurrence time, preoperative T stage, recurrence T stage, BMI, etc. Second-course radiotherapy is defined as radiotherapy administered after tumor recurrence following an initial course of radiotherapy (more than 90 days apart). Diagnosis criteria for postoperative flap necrosis: (1) flap color turns pale, dark purple, or black during endoscopic examination; (2) enhanced MRI suggests poor flap blood supply; (3) confirmed absence of normal blood flow by cutting open part of the flap under endoscopy. This study was approved by the institutional ethics committee of Fujian Cancer Hospital and informed consent was obtained from all patients or their designated proxies. All research was performed in accordance with relevant guidelines/regulations.

Quantitative data with normal distribution are expressed as mean ± standard deviation (± s), analyzed using independent sample t-tests; categorical data are expressed as n (%), analyzed using chi-square tests or Fisher's exact tests. Univariate analysis was first conducted on factors affecting flap prognosis, including age, gender (0 = female, 1 = male), preoperative history of second-course radiotherapy (0 = no, 1 = yes), preoperative EB virus levels, preoperative neutrophil-lymphocyte ratio, albumin, recurrence time (0 = "T < 5 years", 1 = "T ≥ 5 years"), preoperative T stage, recurrence T stage, BMI. Multivariate logistic regression analysis included variables with statistically significant differences from univariate analysis, using the R package "rms" to build the prediction model and plot a nomogram.

We evaluated the model's accuracy using receiver operating characteristic (ROC) curve analysis and calculated the area under the ROC curve (AUC). Internal validation was performed using bootstrap with 1000 repetitions, calculating the mean AUC to assess the model. Decision curve analysis (DCA) was performed using the R package "rmda" to evaluate the clinical utility and net benefit of the nomogram. A P-value < 0.05 was considered statistically significant. SPSS Statistics (version 26.0) and R software (version 4.2.0) were used for analysis.

Clinical Baseline Data: A total of 137 patients were included, with 99 males and 38 females, average age 49.72 ± 9.987 years. Flap survival was observed in 118 cases, with necrosis in 19 cases, resulting in a necrosis rate of 16.1%. Significant differences were found between groups in terms of second-course radiotherapy, initial T stage, recurrence T stage, recurrence time, and postoperative packing time (P < 0.05). No significant differences were observed in age, gender, EB virus levels, BMI, neutrophil-lymphocyte ratio, and albumin levels (P > 0.05) (detailed information in Table 1).

Table 1

Univariate Analysis of Factors Influencing NSF After Salvage Surgery for Recurrent NPC
Factor	NSF survival group	NSF necrosis group	X²(t)	P
Age
<60 years old	104	14	2.861	0.91
≥ 60 years old	14	5
Gender
Female	29	9	4.241	0.039
Male	89	10
Reirradiation
None	115	13	15.698	0.000
Have	3	6
EB virus levels
Normal range	99	14	1.182	0.277
Rising range	19	5
Initial T stage
T1	5	3	8.741	0.033
T2	18	6
T3	72	6
T4	23	4
Recurrent T stage
T1	56	2	9.473	0.024
T2	20	5
T3	32	6
T4	10	6
Recurrence time
<5 years	99	10	9.839	0.002
≥ 5 years	19	9
BMI
<22	43	9	0.830	0.362
≥ 22	75	10
Postoperative packing time
<5 days	39	15	8.694	0.003
≥ 5 days	79	4
Neutrophil to lymphocyte ratio	5.60 ± 0.57	5.44 ± 1.07	0.119	0.905
Albumin levels	40.37 ± 0.36	39.07 ± 1.05	1.312	0.192

Independent Risk Factors for Flap Necrosis: Univariate analysis identified five potential predictive risk factors: second-course radiotherapy, initial T stage, recurrence T stage, recurrence time, and postoperative packing time. Multivariate logistic regression analysis showed that second-course radiotherapy, recurrence T stage, recurrence time, and postoperative packing time were independent risk factors for nasal septum mucosal flap necrosis after salvage surgery for recurrent NPC (P < 0.05) (Table 2). The final formula for the linear relationship was: 0.895 × second-course radiotherapy + 0.296 × recurrence T stage + 0.606 × recurrence time − 0.667 × postoperative packing time + 1.184.

Table 2

Multivariable Logistic Regression Analysis of Factors Influencing NSF After Salvage Surgery for Recurrent NPC
Factor	β	Standard Error	Wald	P	OR	95%CI
Reirradiation	2.121	0.895	5.613	0.018	8.338	1.442–48.197
Initial T stage	−0.440	0.351	1.570	0.210	0.644	0.324–1.282
Recurrent T stage	0.746	0.296	6.328	0.012	2.108	1.179–3.768
Recurrence time	1.479	0.606	5.958	0.015	4.386	1.338–14.378
Postoperative packing time	−1.691	0.667	6.438	0.011	0.184	0.050–0.681
Constant	−2.196	1.184	3.440	0.064	0.111	-

Construction and Validation of the Nomogram: Independent risk factors for flap necrosis (second-course radiotherapy, recurrence T stage, recurrence time, and postoperative packing time) were incorporated into the model to construct a nomogram for predicting the risk of nasal septum mucosal flap necrosis after salvage surgery for recurrent NPC (Fig. 1). The ROC curve and calibration curve were used to evaluate the model's discrimination and calibration. The AUC of the model's ROC curve was 0.736 (95% CI: 0.692–0.781) (Fig. 2A), indicating good discrimination. Internal validation using bootstrap with 1000 repetitions showed a good agreement between the actual and predicted curves (Fig. 2B), indicating good predictive performance. The DCA curve showed significant net benefits for threshold probabilities between 10% and 85% when using this model to predict flap necrosis after salvage surgery for recurrent NPC (Fig. 3).

Nasopharyngeal carcinoma (NPC) is a malignant tumor originating from the epithelial cells of the nasopharynx mucosa, predominantly found in southern China and Southeast Asia. Due to its high sensitivity to radiotherapy, radiotherapy is the preferred treatment for NPC. However, approximately 10.0–36.0% of patients experience disease recurrence after initial treatment[4]. For these recurrent NPC patients, second-course radiotherapy and salvage surgery are the available treatment strategies. Despite second-course radiotherapy offering treatment opportunities for some patients, it is associated with numerous complications and significantly reduced efficacy compared to initial radiotherapy[5]. According to the NCCN guidelines, endoscopic salvage surgery has become the preferred treatment option for all locally recurrent resectable NPC (rNPC) patients[6].

Due to the proximity of the nasopharyngeal lesions to the skull base and the surrounding major blood vessels such as the internal carotid artery, the repair of the surgical wound post-endoscopic salvage surgery for recurrent NPC is crucial to promote healing and protect the surrounding vital vessels. The nasal septal flap (NSF), based on the posterior septal artery branch of the sphenopalatine artery, has been considered an effective and reliable method for repairing postoperative nasopharyngeal wounds [7] and radiation necrosis wounds [8][9]. However, necrosis of the NSF is a significant complication during surgery. This study conducted a detailed analysis of patients with recurrent NPC undergoing endoscopic tumor resection and NSF (alone or in combination with nasal floor mucosal flap) repair, finding an 86.13% survival rate for the NSF, consistent with other studies[10][11]. Additionally, we found that second-course radiotherapy, tumor T stage, and nasal packing time are independent risk factors for NSF necrosis.

Patients undergoing second-course radiotherapy exhibited a significantly higher risk of flap necrosis. Our study found that the probability of NSF necrosis in patients who had undergone second-course radiotherapy was 8.338 times higher than in those who had not. Radiation therapy-induced nasopharyngeal tissue necrosis progresses in three stages: the early stage mainly involves the mucosa, presenting with local degeneration and necrosis; the second stage affects the mucosa and muscles, extending to the nasopharyngeal muscles and causing significant defects in the parapharyngeal space; the third stage manifests as skull base radiation osteonecrosis[12]. Most recurrent NPC patients who undergo radiation therapy experience at least the early stage of nasopharyngeal necrosis, affecting blood perfusion in the nasopharyngeal area. Second-course radiotherapy exacerbates this condition. After flap transplantation, in addition to the blood supply from the pedicle vessels, the flap also requires the establishment of new capillary networks with the surrounding tissue or base for nourishment, increasing the complexity of this process in the presence of nasopharyngeal disease. The nasal septal flap (NSF) based on the posterior septal artery, located in the radiation target area for NPC, may suffer from radiation-induced changes in blood flow and tissue degeneration, reducing flap survival. Studies indicate that second-course radiotherapy is an independent risk factor for post-radiation nasopharyngeal necrosis (PRNN) in recurrent NPC patients [13] and an independent risk factor for the non-epithelialization of the nasopharyngeal area after NSF repair[14]. Therefore, stricter evaluations are warranted when using NSF for repair in patients who have undergone second-course radiotherapy.

Our study indicates an association between later T stage recurrence and flap necrosis. Advanced T stage tumors usually involve more extensive local invasion, necessitating wider tissue resection and flap repair. As the flap size increases, the distance between the distal part of the flap and the pedicle vessels lengthens, challenging blood supply to the distal flap. Researchers have found that advanced T stage is a risk factor for poor healing of the nasal septal flap[15], and flap size is an independent risk factor for complications after reconstructive surgery[16]. Therefore, tumor staging must be considered when planning surgery and selecting flaps. While the NSF can provide blood supply within the range of the nasal septum and nasal floor mucosa, its coverage area is limited, which may be insufficient for large defects, especially when distal blood supply is compromised. For advanced T stage patients, NSF might not be the best choice for postoperative defects. Instead, the temporalis muscle flap, offering a larger tissue volume and located outside the radiation target area for NPC, could provide better coverage and blood supply for large defects after advanced T stage tumor surgery[17] .

Our study reveals that the time of NPC recurrence is a high-risk factor affecting flap survival. Patients with longer recurrence times have a higher risk of NSF necrosis compared to those with shorter recurrence times. This could be related to the effects of radiotherapy. Radiotherapy causes both acute and late toxic reactions, with late toxic reactions including radiation-induced oral mucositis, xerostomia, dysphagia, radiation caries, radiation-induced osteonecrosis of the jaw, cranial nerve damage, temporal lobe necrosis, hypothyroidism, carotid atherosclerosis, muscle fibrosis, and radiation skin reactions. Although symptoms like xerostomia may gradually alleviate over time, issues such as hearing loss, nutritional deficiencies, tissue fibrosis, and neurological damage may worsen with time[18]. Therefore, radiotherapy may cause vascular and microcirculatory damage to the nasopharynx and nasal septum mucosa in recurrent NPC patients, which could gradually worsen over time. Surgical intervention may further reduce tissue tolerance and healing ability, leading to insufficient blood supply to the nasopharynx and NSF, increasing the risk of necrosis. Studies show that a short interval between radiotherapy and salvage pharyngolaryngeal surgery may increase the risk of complications in microvascular free tissue transfer[19]. Therefore, in patients with long-term NPC recurrence, special attention should be paid to evaluating the long-term effects of radiotherapy and taking measures to reduce the risk of necrosis during flap repair surgery.

The duration of nasal packing affects flap survival. Nasal packing for less than 5 days presents a higher risk of NSF necrosis compared to packing for 5 days or more. The fit between the NSF and the nasopharyngeal defect is a crucial factor affecting NSF survival [20]. Shorter nasal packing times may result in poor NSF adherence, leading to NSF necrosis. While longer packing times may improve NSF adherence, they could also cause poor local blood circulation, adversely affecting flap blood supply and healing. Therefore, reasonable control of nasal packing time during surgery is essential to improve flap survival and reduce the risk of complications, finding a balance between ensuring good flap adherence and maintaining adequate local blood circulation. Our experience suggests that 8 days is an ideal nasal packing time for NSF post-surgery.

This study developed a predictive model to assess the risk of NSF necrosis in recurrent NPC patients undergoing endoscopic resection and flap repair surgery. This model integrates factors such as radiotherapy history, recurrence T stage, recurrence time, and postoperative packing time to minimize the complications of flap necrosis. However, the study has some limitations. First, it is a retrospective analysis, which is less robust than a prospective analysis. Second, the sample size is small. NPC is mainly prevalent in southern China and Southeast Asia, limiting the study's geographic scope. The complex anatomy of the skull base and the high technical threshold for salvage surgery in recurrent NPC further limit the patient sample size. Additionally, the lack of external validation limits the generalizability and strength of the study's conclusions.

In conclusion, second-course radiotherapy, recurrence T stage, recurrence time, and postoperative packing time are identified as independent risk factors for NSF necrosis following salvage surgery for recurrent NPC. The risk assessment system based on these factors demonstrates good predictive ability, helping clinicians make more precise decisions in planning and implementing salvage surgery for recurrent NPC patients. This assessment system aids in identifying high-risk patients, enabling targeted treatment strategies and monitoring plans to reduce the risk of flap necrosis, improve surgical success rates, and enhance patient quality of life.

This study successfully established a predictive model incorporating four key variables: second-course radiotherapy history, recurrence T stage, recurrence time, and postoperative packing time. This model effectively identifies high-risk situations for NSF necrosis in recurrent NPC patients undergoing salvage surgery, providing a basis for clinicians to implement targeted interventions to reduce the risk of complications and improve treatment success rates.

Author Contributions

Youyuan Shi conceived and designed the research; Qilin Gong and Huaying Li analyzed and wrote the manuscript; Hui Liu collected and analyzed the data; All authors edited and approved the manuscript.

Disclosure

Competing interests:The authors declare no competing interests.

Funding source:

This work was supported by the Natural Science Foundation of Fujian Province, China (Grant No. 2021J01447), Joint Funds for the Innovation of Science and Technology,Fujian provence, China (Grant No. 2023Y9429).

Data availability

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

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You are reading this latest preprint version

Clinical Prediction Model for Necrosis of Nasal Septum Mucosal Flap After Salvage Surgery for Recurrent Nasopharyngeal Carcinoma

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Methods

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Conclusion

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Introduction

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Conclusion

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