Patterns of failure and clinical outcomes of post-operative buccal mucosa cancers treated with adjuvant ipsilateral radiotherapy.

PURPOSE: Adjuvant radiotherapy (RT) in buccal mucosa cancers is guided by histopathological factors. The decision to treat ipsilateral or bilateral draining lymph node is on physician discretion and guidelines do not have a defined indication regarding this. We aimed to analyze the failure patterns and survival in buccal mucosa cancers treated with adjuvant ipsilateral RT. MATERIALS AND METHODS: One hundred sixteen cases of post-operative buccal mucosa cancers-pT3 or more, node positive, close margins (1-5 mm), lymphovascular invasion positive, perineural invasion positive, depth of invasion >4 mm-treated with RT to primary and ipsilateral nodes from May 2013 to May 2019 were retrospectively analyzed. Patients were treated to a dose of 60-66 Gy (44 Gy in the first phase and a coned down boost of 16-22 Gy in the second phase) with three-dimensional conformal radiotherapy on a linear accelerator. Primary end point was to assess control rates and secondary end point was to evaluate the overall survival (OS) and disease-free survival (DFS) outcomes. RESULTS: Median age was 46 years with male; female ratio of 110:6. The edition of the American Joint Committee on Cancer stage distributions were I (3.4%), II (34.4%), III (24.1%), and IV (37.9%). At a median follow-up of 22 months, crude rates of local failure, regional failure, and contralateral neck failure were 9.4%, 10.3%, and 3.4%, respectively. The 2-year contralateral neck control rate was 94.9%. Pathological positive node portended poorer OS (86.6% vs. 68.6%; p = 0.015) and DFS (86.5% vs. 74.9%; p = 0.01). CONCLUSION: Incidence of contralateral recurrence with ipsilateral irradiation in buccal mucosa cancers is low with descent survival outcomes, particularly in node negative cases.