Several strategies have been investigated to improve the 4% survival advantage of adjuvant chemotherapy in early-stage non-small-cell lung cancer (NSCLC). In this investigator-initiated study we aimed to evaluate the predictive utility of the messenger RNA (mRNA) expression levels of excision repair cross complementation group 1 (ERCC1) and thymidylate synthase (TS) as assessed in resected tumor. Seven hundred and seventy-three completely resected stage II-III NSCLC patients were enrolled and randomly assigned in each of the four genomic subgroups to investigator’s choice of platinum-based chemotherapy (C, n = 389) or tailored chemotherapy (T, n = 384). All anticancer drugs were administered according to standard doses and schedules. Stratification factors included stage and smoking status. The primary endpoint of the study was overall survival (OS). Six hundred and ninety patients were included in the primary analysis. At a median follow-up of 45.9 months, 85 (24.6%) and 70 (20.3%) patients died in arms C and T, respectively. Five-year survival for patients in arms C and T was of 65.4% (95% CI (confidence interval): 58.5% to 71.4%) and 72.9% (95% CI: 66.5% to 78.3%), respectively. The estimated hazard ratio (HR) was 0.77 (95% CI: 0.56-1.06, P value: 0.109) for arm T versus arm C. HR for recurrence-free survival was 0.89 (95% CI: 0.69-1.14, P value: 0.341) for arm T versus arm C. Grade 3-5 toxicities were more frequently reported in arm C than in arm T. In completely resected stage II-III NSCLC tailoring adjuvant chemotherapy conferred a non-statistically significant trend for OS favoring the T arm. In terms of safety, the T arm was associated with better efficacy/toxicity ratio related to the different therapeutic choices in the experimental arm. •Adjuvant platinum-based chemotherapy is accepted as standard of care in stage II and III (NSCLC) patients.•Several studies addressed the question of whether molecular tumor markers may serve as predictive biomarkers.•ITACA was planned to evaluate the predictive utility of ERCC1 and TS mRNA expression levels in completely resected NSCLC.•ITACA results indicate that adjuvant chemotherapy customization based on ERCC1 and TS mRNA levels did not improve efficacy.•In terms of safety, the pharmacogenomic-driven arm was associated with better efficacy/toxicity ratio.