The effects of hemoglobin levels and their interactions with cigarette smoking on survival in nasopharyngeal carcinoma patients

There is very little published information regarding the prognostic value of hemoglobin (Hb) levels combined with smoking on the survival of patients with nasopharyngeal carcinoma (NPC), and the interactions between them remain unclear. A total of 2440 NPC patients were confirmed, and multivariate analysis was performed to identify valuable prognostic Hb levels in the entire population and in the cohort of smokers. The survival differences were compared using log-rank tests. The multiplicative and additive interactions were assessed using Cox regression and a Microsoft Word Excel spreadsheet. Postradiotherapy (RT) Hb was an independent prognostic factor for overall survival (OS) (HR = 0.797; P = 0.006), failure-free survival (FFS) (HR=0.811; P = 0.010), and loco-regional failure-free survival (LR-FFS) (HR = 0.725; P = 0.000). In the cohort of smokers, pack-years was also an independent predictor of OS (HR = 0.673; P < 0.001) and FFS (HR = 0.681; P < 0.001), LR-FFS (HR = 0.663; P = 0.001). A significant positive additive effect was found for the interaction between low post-RT Hb and high SI on OS, with RERI = 5.616, AP = 0.665, and S = 4.078. Stratified analyses demonstrated that heavy smokers with low post-RT Hb had HRs of 2.295 (P < 0.001) for death, 2.222 (P < 0.001) for disease failure, and 2.267 (P < 0.001) loco-regional recurrence compared with light smokers with high post-RT Hb levels, and post-RT Hb level is an important predictor of survival in patients with NPC. The positive interaction between post-RT Hb level and pack-years contributes to the elevated risk of poor survival. Oncologists should devote particular attention to heavy smokers with low post-RT Hb levels in the future.