Smoking exposure and overall survival in nasopharyngeal carcinoma: a multicenter cohort from non-endemic northern China with an exploratory meta-analysis

Smoking exposure is routinely documented in nasopharyngeal carcinoma (NPC), but its prognostic relevance in non-endemic regions is uncertain. We analyzed a multicenter retrospective cohort of 1022 patients with non-metastatic NPC treated with definitive-intent intensity-modulated radiotherapy in northern China using Kaplan–Meier and multivariable Cox methods, and conducted a secondary exploratory meta-analysis of seven published studies reporting adjusted overall-survival estimates. Among 980 patients with known smoking status, 244 were never, 182 former, and 554 current/recent smokers. Five-year overall survival was 83.0%, 80.6%, and 74.9%, respectively. After adjustment for age, sex, late-stage disease, hospital tier, diagnosis year, and diagnostic delay, the adjusted HRs were 1.35 for current/recent versus never smoking (95% CI 0.97–1.88; P = 0.074) and 1.31 for ever versus never smoking (95% CI 0.96–1.79; P = 0.094). The meta-analysis yielded a pooled adjusted HR of 1.96 (95% CI 1.41–2.73; I-squared = 74.5%). In the multicenter cohort, smoking was associated with poorer unadjusted survival; however, the fully adjusted estimates were attenuated and imprecise. Published adjusted estimates indicated higher mortality hazards but substantial between-study heterogeneity. These observational findings warrant cautious interpretation and more standardized smoking assessment.