Impact of radiation interruption and associated factors on overall survival in head and neck cancer at Tikur Anbessa Specialized Hospital, Ethiopia.

e18058 Background: Unplanned interruption in radical radiotherapy for head and neck squamous cell carcinoma is associated with poorer outcome. In Ethiopia, however, the effect of interruption and contributing factors on overall survival have not been well-studied. Methods: We retrospectively analyzed the records of 126 patients enrolled for radical radiotherapy using a linear accelerator in our tertiary hospital from May 2021 to February 2024. We summarized all of the relevant information such as patient characteristics, treatment received, treatment outcomes, overall treatment time, as well as more information of treatment interruption were collected. Overall survival was estimated using the Kaplan-Meier method and verified by log-rank test. Variables with a log-rank value < 0.05 were considered significant associations. Results: Most patients were in the age group of 37-61 years with males comprising 64.3% of cases. The Nasopharynx was the most common subsite involved (50%) followed by the oral cavity (20.63%) and the larynx (15.08 %). The average radiotherapy dose prescribed was 68.71Gy (SD±3.262), while the average dose received was 62.36Gy (SD±14.604). Concurrent chemoradiation was given to 43% of patients. The mean radiotherapy treatment time (RTT), including interruptions, was 49 days, while the average interruption duration was 8 days. Treatment interruption occurred in 82.5 %, of which radiotherapy machine-related issues contributed to 44.5% followed by holiday at 34.86%. Approximately 50% of patients experienced multiple interruptions during treatment. The proportion of patients with treatment interruption time ≤ 5 days was 58 (49.6 %). At the time of this retrospective review, 77 patients (61.11%) were alive, with a median follow-up of 13 months, while 38(30.6%) patients died. The 1-year overall survival rate of all patient’s cohort was 65% (95%CI 57.2,75.3). Univariate and multivariate analysis showed radiation break and duration of interruption exceeding 5 days were a significant prognostic factors for overall survival. The presence of radiation break was a 2.65 times increased risk chance of poor survival compared to those without interruption (HR=2.654, 1.313-6.725, P=0.025). In addition, longer than 5 days length of interruption was an independent predictor of poor survival compared to interruption less than 5 days (HR=2.036, 1.009-4.1017, P=0.031). Conclusions: The presence of radiation break and the length of interruption exceeding 5 days are independent predictors of poor overall survival in head and neck squamous cell cancer patients undergoing radical radiotherapy. We should minimize the interruption of radiotherapy whenever possible to improve patients' outcomes.