Validation of patient's self-reported social functioning as an independent prognostic factor for survival in metastatic colorectal cancer patients:: results of an international study by the Chronotherapy Group of the European Organisation for Research and Treatment of Cancer

Purpose A recent study identified a prognostic model for survival in metastatic colorectal cancer patients which included WBC count, alkaline phosphatase (AP), number of metastatic sites, and patients' self-reported social functioning. The aim of this research is to validate this model on data from an independent sample. Patients and Methods This validation study is based on a prospective randomized controlled trial in patients with metastatic colorectal cancer conducted by the European Organisation for Research and Treatment of Cancer (EORTC) Chronotherapy Group. Overall, 564 patients in 10 countries were enrolled. For the purpose of this independent validation, patients with health-related quality of life (HRQOL) baseline data were analyzed. HRQOL was assessed using the EORTC Quality of Life Questionnaire C30 (QLQ-C30). The Cox proportional hazards regression model was used for both univariate and multivariate analyses of survival. Results The previous model with an additional adjustment, by stratification for sex, was replicated and its parameters were confirmed to independently predict survival: WBC count with an hazard ratio (HR) of 1.31 (95% CI, 1.021 to 1.698; P = .034); AP with an HR of 1.53 (95% CI, 1.188 to 1.979; P = .001); number of sites involved with an HR of 1.90 (95% CI, 1.531 to 2.364; P < .0001); and patients' self-reported social functioning with an HR of 0.94 (95% CI, 0.905 to 0.976; P = .001). The latter translates into a 6% increase in the likelihood of an earlier death for every 10-point decrease in the social functioning scale of the EORTC QLQ-C30. Conclusion This study provides confirmatory evidence of the independent prognostic value of patients' self-reported social functioning in patients with advanced colorectal cancer.