Radiation dose escalation for local advanced nasopharyngeal carcinoma patients with locally and/or regionally residual lesions after standard chemoradiotherapy

Purpose: To assess the effectiveness and toxicity of radiation dose escalation in treating local advanced nasopharyngeal carcinoma patients (LA-NPCs) who have locally and/or regionally residual lesion(s) after standard treatment. Methods and materials: From November 2011 to November 2020, 259 LA-NPCs with residual local and/or regional lesion(s) after receiving induction chemotherapy followed by concurrent chemoradiotherapy (IC + CCRT) from our hospital were included. The total dose of primary radiotherapy (RT) was 68.1-74.25 Gy (median, 70.4 Gy). The boost doses were 4.0–18.0 Gy (median, 9 Gy), 1.8-2.0 Gy/fraction. Results Five-year local relapse-free survival (LRFS), regional relapse-free survival (RRFS), locoregional relapse-free survival (LRRFS), distant metastasis-free survival (DMFS), failure-free survival (FFS) and overall survival (OS) for all patients were 90.2%, 89.1%, 79.5%, 87.9%, 69.0%, 86.3%, respectively. LRRFS, DMFS, FFS, and OS in patients with age ≤ 65 versus > 65, plasma EBV-DNA ≤ 500 versus > 500, T 1 − 2 versus T 3 − 4 , N 0 − 1 versus N 2 − 3 , and stage III versus stage IV showed no statistically significant differences. The interval between primary RT and boost was not a prognostic factor for LRRFS, DMFS, FFS, and OS. Males had a lower 3-year FFS rate than females (72.9% vs. 83.7%, P = 0.024). LA-NPCs with locally and regionally residual lesion(s) had the worst 3-year DMFS and OS rates compared with locally or regionally residual lesion(s) (77.7% vs. 98.8% vs. 87.4%, P = 0.014; 75.9% vs. 94.5% vs. 82.4%, P = 0.002). Conclusion Boost radiation was an option for LA-NPCs with locally and/or regionally residual lesions after receiving IC + CCRT. It warrants further prospective study.