Radiation-induced xerostomia and oncologic outcomes in nasopharyngeal carcinoma treated with comprehensive salivary gland-sparing helical tomotherapy: a prospective study of 266 patients

Objective To evaluate whether comprehensive salivary gland–sparing helical tomotherapy (HT) can reduce radiation-induced xerostomia without compromising locoregional control or survival in patients with nasopharyngeal carcinoma (NPC). Methods A total of 266 patients with NPC treated with HT were prospectively analyzed. A comprehensive salivary gland–sparing planning strategy, including preservation of the parotid glands and other salivary structures whenever clinically feasible, was applied to minimize irradiation of salivary glands. Xerostomia was assessed using patient-reported outcome measures during follow-up. Acute and late toxicities were graded according to the RTOG/EORTC criteria. Overall survival (OS), cancer-specific survival (CSS), locoregional recurrence-free survival (LRRFS), and distant metastasis-free survival (DMFS) were estimated using the Kaplan–Meier method. Results With a median follow-up of 70.5 months, patients showed significant improvement in xerostomia symptoms. Late xerostomia was observed in 26 patients (9.8%) with Grade I–II, and only one patient (0.4%) developed Grade III xerostomia. The 1-, 3-, and 5-year overall survival (OS) rates were 95.9%, 86.8%, and 81.6%, respectively, while the corresponding cancer-specific survival (CSS) rates were 98.1%, 92.6%, and 90.2%. Locoregional control remained excellent, with a locoregional recurrence rate of 7.5% and a 5-year locoregional recurrence-free survival (LRRFS) of 92.1%. No grade 4 acute or late toxicity was observed. Multivariate Cox regression analysis demonstrated that age was significantly associated with survival outcomes (OS: p = 0.01; CSS: p = 0.01). Conclusions Comprehensive salivary gland-sparing helical tomotherapy reduces radiation-induced xerostomia without compromising locoregional control or survival, supporting its oncologic safety in NPC radiotherapy. Clinical trial registration https://www.chictr.org.cn/showproj.html?proj=17360 , identifier ChiCTR-ONN-17010597.