Cutoff point of neutrophil-to-lymphocyte ratio for predicting survival in nasopharyngeal carcinoma

Neutrophil-to-lymphocyte ratio (NLR) was reported as an independent prognostic factor in many studies, but its cutoff point was not yet concluded. We set forth to prove and validate cutoff point of NLR as a poor prognostic factor for overall survival (OS) in nonmetastatic nasopharyngeal carcinoma (NPC) patients. Retrospective cohort of nonmetastatic NPC adult patients treated with intensity-modulated radiotherapy with curative aim at Siriraj hospital during 2007 to 2014 was enrolled. NLR was defined as absolute neutrophil count divided by absolute lymphocyte count. OS was the primary outcome. We explored our cutoff value by maximum concordance index (C-index) method, and we validated our cutoff and previously reported cutoff values by categorizing patients as NLR <= 3 or >3. Internal validation was done by bootstrapping method. Four hundred sixty-three patients were included. The median follow-up time was 70.8 months. By the end of June 2019, 211 patients had died. In univariable analysis of OS by Cox model, an NLR value of 3 showed the highest C-index (0.548) with an HR of 1.43 (95% CI: 1.08-1.89). After adjustment for body mass index, overall staging, age, gender, and histology in multivariable analysis, an NLR >3 was still an independent prognostic factor of poor OS (HR = 1.34, 95% CI = 1.01-1.79). After internal validation, the resampling method shows no overfitting condition and corrected C-index was 0.547 for univariable analysis. A cutoff point of NLR of 3 from routine blood test was found to be an independent poor prognostic factor among patients with nonmetastatic NPC. This prognostic factor could be included in clinical prediction model of NPC and this further prediction model would select high risk patients for intensive treatment.