Cross-validation study of class III beta-tubulin as a predictive marker for benefit from adjuvant chemotherapy in resected non-small-cell lung cancer: analysis of four randomized trials

Abstract

The IALT, JBR.10, ANITA and Cancer and Leukemia Group B 9633 trials compared adjuvant chemotherapy with observation for patients with resected non-small-cell lung cancer (R-NSCLC). Data from the metastatic setting suggest high tumor class III beta-tubulin (TUBB3) expression is a determinant of insensitivity to tubulin-targeting agents (e.g. vinorelbine, paclitaxel). In 265 patients from JBR.10 (vinorelbine-cisplatin versus observation), high TUBB3 was an adverse prognostic factor and was associated (nonsignificantly) with 'greater' survival benefit from chemotherapy. We explored this further in additional patients from JBR.10 and the other three trials. TUBB3 immunohistochemical staining was scored for 1149 patients on the four trials. The original JBR.10 cut-off scores were used to classify tumors as TUBB3 high or low. The prognostic and predictive value of TUBB3 on disease-free survival (DFS) and overall survival (OS) was assessed by Cox models stratified by trial and adjusted for clinical factors. High TUBB3 expression was prognostic for OS [hazard ratio (HR)=1.27 (1.07-1.51), P=0.008) and DFS [HR=1.30 (1.11-1.53), P=0.001). TUBB3 was not predictive of a differential treatment effect [interaction P=0.20 (OS), P=0.23 (DFS)]. Subset analysis (n=420) on vinorelbine-cisplatin gave similar results. The prognostic effect of high TUBB3 expression in patients with R-NSCLC has been validated. We were unable to confirm a predictive effect for TUBB3.