Radiation dose escalation for locally advanced nasopharyngeal carcinoma patients with local and/or regional residual lesions after standard chemoradiotherapy: a non-randomized, observational study

BACKGROUND: To assess the effectiveness and toxicity of radiation dose escalation for locally advanced nasopharyngeal carcinoma (LA-NPC) in patients with local and/or regional residual lesion(s) after standard treatment. METHODS: From November 2011 to November 2020, 259 LA-NPC patients who had local and/or regional residual lesion(s) after 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: For all patients, the 5-year local relapse-free survival was 90.2%, regional relapse-free survival was 89.1%, locoregional relapse-free survival (LRRFS) was 79.5%, distant metastasis-free survival (DMFS) was 87.9%, failure-free survival (FFS) was 69.0%, and overall survival (OS) was 86.3%. LRRFS, DMFS, FFS, and OS in patients with age ≤ 65 versus > 65, plasma Epstein-Barr virus-deoxyribonucleic acid ≤ 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. Trial registration: Retrospectively registered.