Effectiveness and risk of second primary malignancies after radiotherapy in major salivary gland carcinomas: A retrospective study using SEER database.

ABSTRACT

OBJECTIVE: To investigate the effectiveness of radiotherapy and its association with second primary malignancies (SPMs) risk in major salivary gland carcinomas (MSGCs) patients. METHODS: Cohort 1 included 7274 surgically treated MSGC patients from the Surveillance, Epidemiology, and End Results database, assessing the effectiveness of radiotherapy. Cohort 2 (n = 4213) comprised patients with ≥5-year survival in Cohort 1 to study SPMs. RESULTS: Radiotherapy decreased overall survival in MSGCs patients, but improved it in high-grade MSGCs. Cumulative SPMs incidences at 25 years were 16.5% in the radiotherapy (RT) group compared to 14.5% in the non-radiotherapy (NRT) group. For second head and neck carcinomas (SHNCs), incidences were 3.4% in RT versus 1.6% in NRT. Radiotherapy increased the relative risks of tumors, particularly SHNCs (RR = 1.78). The 10-year OS rates of SHNCs after radiotherapy were significantly lower. CONCLUSION: Radiotherapy improves survival in advanced-stage MSGCs but increases the risk of developing SPMs, particularly SHNCs.