Result of the 6-min walk test is an independent prognostic factor of surgically treated non-small-cell lung cancer

Abstract

Objectives: Pathological tumour, node and metastasis (TNM) stage remains the most significant prognostic factor of non-small-cell lung cancer (NSCLC). Meanwhile, age, gender, pulmonary function tests, the extent of surgical resection and the presence of concomitant diseases are commonly used to complete the prognostic profile of the patient with early stage of NSCLC. The aim of this study is to assess how the result of a 6-min walk test (6MWT) further assists in predicting the prognosis of NSCLC surgical candidates. Methods: Six hundred and twenty-four patients who underwent surgical treatment for NSCLC between April 2009 and October 2011 were enrolled in this study. All patients were accepted for surgery on the basis of a standard evaluation protocol. Additionally, patients completed the 6MWT on the day before the surgery, and threshold values of the test were assessed based on both the Akaike information criterion and the coefficient of determination R2. Cox proportional hazards regression analysis was used to analyse the effect of important prognostic factors on the overall survival. Results: Three hundred and ninety men and 234 women with a mean age of 64 years underwent radical surgical treatment for primary lung cancer. Five hundred and twenty-five lobectomies (84%), 77 pneumonectomies (12%) and 24 (4%) lesser resections were performed. Three hundred and thirty-one patients (53%) were treated for stage I NSCLC, 191 patients (31%) for stage II and 102 patients (16%) for stages IIIA-IV. A distance of 525 m in the 6MWT [hazard ratio (HR) = 0.57, 95% confidence interval (CI) 0.41-0.78, P < 0.001] was the threshold value differentiating the patients' prognoses (P < 0.001). Using the Cox proportional hazards regression analysis, pathological TNM stage (IIA: HR = 1.87, 95% CI 1.95-2.92, P = 0.006; IIB: HR = 2.03, 95% CI 1.23-3.37, P = 0.006; IIIA-IV: HR = 2.37, 95% CI 1.49-3.75, P < 0.001), male gender (HR = 1.88, 95% CI 1.26-2.79, P = 0.001), pneumonectomy (HR = 1.78, 95% CI 1.17-2.70, P < 0.001) and the results of the 6MWT (HR = 0.50, 95% CI 0.36-0.70, P < 0.001) were considered as independent predictive factors of overall survival. Conclusions: The result of a 6MWT is an independent and convenient prognostic factor of surgically treated non-small-cell lung cancer.