Clinical Efficacy of Adjuvant Chemotherapy in Stage IB (<4cm) Non-Small Cell Lung Cancer Patients with High-Risk Factors.

Background/Aims Adjuvant chemotherapy is the standard of care for resected stage II-IIIA non-small cell lung cancer (NCSLC). The efficacy of adjuvant chemotherapy in stage IB (<4cm) NSCLC with high-risk factors remains controversial. Methods This was a retrospective multi-center study of four academic hospitals. We analyzed 285 stage IB NSCLC patients with high-risk factors according to the 8th edition TNM classification. High-risk factors were visceral pleural invasion, vascular invasion, lymphatic invasion, lung neuroendocrine tumors, and micropapillary histology pattern. Results Of the 285 cases, 127 (44.6%) were in the adjuvant chemotherapy group and 158 (55.4%) were in the non-adjuvant chemotherapy group. Median follow-up was 41.5 months. Adjuvant chemotherapy significantly reduced the recurrence rate compared to the control group (Hazards ratio, 0.408; 95% Confidence interval, 0.221-0.754; P = 0.004) and the risk of death compared to the control group (Hazards ratio, 0.176; 95% Confidence interval, 0.057-0.546; P = 0.003). Among the various high-risk factors, adjuvant chemotherapy should be more considered if there were visceral pleural involvement or vascular invasion. Based on the subgroup analysis, adjuvant chemotherapy should also be considered when visceral pleural involvement is present even if the tumor size is less than 3cm. Conclusions Adjuvant chemotherapy may be useful for patients with stage IB NSCLC with high-risk factors and more relevant for patients with visceral pleural involvement or vascular invasion.