Interaction between treatment delivery delay and stage on the mortality from non-small cell lung cancer

Background: The aim of this study is to evaluate the interaction between treatment delay and stage on the mortality from non-small cell lung cancer (NSCLC). Methods: We performed a survival analysis in a cohort of patients admitted to the reference cancer center. The following data were collected: age, gender, smoking status, tumor staging, type of lung cancer, and time from the date when the patient was diagnosed with cancer to the starting date of effective treatment. Univariable and multivariable Cox proportional hazard models were used to investigate the association between potential confounders identified during the study design. After the final adjusted model was determined, tests for interaction among all predictors were performed. Results: Inclusion criteria were met by 359 patients. In the adjusted analysis, delayed treatment delivery was a protective factor for the risk of death, with a crude hazard ratio (HR) = 0.75 (0.59-0.97; P=0.02) and an adjusted HR = 0.59 (0.46-0.77; P<0.001). However, a statistically significant interaction with mortality was observed between timely treatment and tumor stage. Patients with stage II disease who received delayed treatment had a higher risk of death [HR = 3.08 (1.05-9.0; P=0.04)]. On the other hand, stage IV patients who received delayed treatment had a 52% reduction in mortality [HR = 0.48 (0.35-0.66; P<0.001)]. Conclusions: Stage of disease influenced the association between start of the treatment and mortality, and only the subgroup of stage II patients seemed to benefit from early treatment.