Treatment outcomes and failure patterns in postoperative radiotherapy for major salivary gland carcinoma.

Objective: Surgery is the standard of care for major salivary gland carcinoma (MSGC), and postoperative radiotherapy (PORT) is used for patients at high risk of postoperative recurrence.

Methods: We retrospectively analyzed 32 patients with MSGC treated with PORT between 2010 and 2019. All patients had one or more of the following high-risk factors for recurrence: histologically high-grade, T3-4 tumors, positive or close margins, lymph node (LN) metastasis, and perineural invasion.

Results: The median age of the patients was 63 years (range, 18-81 years). Stage I, II, III, and IV disease were observed in 2, 5, 7, and 18 patients, respectively. Twenty-two patients underwent concurrent systemic therapy. The most commonly irradiated areas were the primary lesion and ipsilateral neck (78%). The 5-year overall survival (OS), recurrence-free survival (RFS) and locoregional control rates were 49%, 31%, and 77%, respectively. The 5-year OS rates were 86% for Stages I-III, and 22% for Stage IV. The 5-year RFS rates were 57% for Stages I-III, and 11% for Stage IV. Recurrence occurred in 22 patients. The most common pattern of recurrence was pulmonary metastases (34%). There were seven cases of cervical LN metastasis at the time of first recurrence, and five of these cases showed cervical LN metastases outside the irradiated area.

Conclusions: We reported the results of PORT in patients with MSGC. Although the incidence of in-field recurrence was low, recurrence from outside the irradiated area was common, suggesting the need for further investigation into the optimal systemic therapy and radiation extent.