Radiation-induced second primary squamous cell carcinoma of the oral cavity after radiotherapy for nasopharyngeal carcinoma

Background: The increasing occurrence of radiation-induced second primary squamous cell carcinoma of the oral cavity (RISCCO) after radiotherapy for nasopharyngeal carcinoma (NPC) has become a noteworthy complication that can influence long-term survival. This study aimed to analyze the associations of clinicopathologic characteristics with prognostic factors among patients who developed RISCCO after radiotherapy for NPC. Methods: A total of 41,446 NPC patients admitted to Sun Yat-sen University Cancer Center (SYSUCC) between August 1989 and January 2019 were reviewed. Among these patients, 88 RISCCO patients who satisfied the inclusion criteria were included in the study. Results: During our study, the incidence of RISCCO after radiotherapy was 0.21% (88/41,446) among NPC patients at SYSUCC. The latency period ranged from 1.0 to 34.0 years (median, 9.0 years), and the latency of RISCCO was notably shorter for patients who received intensity-modulated radiation therapy than that for patients who received conventional radiotherapy using cobalt-60 or 6-MV X-rays (median, 4.0 years vs. 11.0 years, P = 0.013). The 1-, 3-, and 5-year overall survival (OS) rates for the entire cohort of 88 patients were 79.0%, 46.6%, and 35.2%, respectively. The 5-year OS rate for the 79 patients who received treatment was 45.7%, and the 5-year OS rate for the 9 patients who refused treatment was 0%. T classification and surgery were identified as independent prognostic factors associated with a high OS rate. Conclusions: Surgery as the first-choice treatment may improve survival and prognosis. A long-term follow-up is needed for early detection of RISCCO in NPC patients.