Propensity-matched analysis of adjuvant chemotherapy for completely resected Stage IB non-small-cell lung cancer patients

Background The use of adjuvant chemotherapy (ACT) in completely resected stage IB non-small cell lung cancer (NSCLC) is still controversial. The divergent outcomes of prospective trials have created uncertainty as to the utility of ACT in stage IB NSCLC. This study assesses the effect of postoperative adjuvant chemotherapy in stage IB patients in clinical practice. Methods: Patients with pT2aNOMO stage IB NSCLC who underwent complete resection from 2004 to 2015 were identified from prospectively collected databases in two medical centers. The log-rank test was used to compare overall survival (OS) and disease free survival (DFS). Fine and Gray's competing risks regression model was built to identify predictors of cancer-specific survival. One to one propensity-score matching (PSM) was performed to reduce the selection bias and additional analyses were performed on these subgroups. Results: Of 1005 patients identified for the study, 202 (20.1%) received ACT and 803 (79.9%) underwent surgery alone (observation group). Compared with the observation group, patients who underwent ACT were younger (p < 0.001), had larger tumors (p = 0.004), and had higher rates of squamous cell carcinoma (p < 0.001) and lymphovascular invasion (p = 0.017). After propensity score matching, 196 pairs of patients were 1:1 matched in the two groups and all baseline characteristics were well balanced. ACT was not associated with improved survival (including OS, DFS; all log-rank p > 0.05) in both unmatched and matched (196 pairs) cohorts. In subgroup analysis of the matched population, ACT was not associated with survival benefits for patients regardless of whether their tumors measured < 4 cm or >= 4 cm (both log-rank p > 0.05). Conclusions: In patients with completely resected stage IB (T2aNOMO) NSCLC, ACT is not associated with improved prognosis. Further large multicenter studies are needed to confirm these findings.