A multi-institutional, randomized, phase III trial comparing anatomical segmentectomy and lobectomy for clinical stage IA3 pure-solid non–small-cell lung cancer: West Japan Oncology Group study WJOG16923L (STEP UP trial).

TPS8123 Background: Recent pivotal clinical trials, conducted by the Japan Clinical Oncology Group and West Japan Oncology Group (JCOG0802/WJOG4607L) or Cancer and Leukemia Group B (CALGB140503), have demonstrated the efficacy of anatomical segmentectomy for small-sized early-stage NSCLC measuring ≤ 2 cm. Segmentectomy is gaining attention as an alternative procedure to lobectomy for early-stage NSCLC. However, for tumors larger than 2 cm, particularly those with a pure-solid appearance which indicates higher malignant potential, the efficacy of segmentectomy remains controversial. Therefore, we initiated this randomized phase III trial (WJOG16923L: STEP UP) to confirm the non-inferiority of anatomical segmentectomy to lobectomy for patients with pure-solid NSCLC measuring > 2 cm and ≤ 3 cm. Methods: This multi-institutional, open-label, randomized phase III study is designed to confirm the non-inferiority of anatomical segmentectomy to lobectomy in terms of overall survival (OS) in patients with clinical stage IA3 pure-solid peripheral NSCLC (tumor’s center located in the outer third of the lung field, tumor measuring > 2 cm and ≤ 3 cm, and consolidation-to-tumor ratio = 1). Patients are randomized 1:1 to undergo either lobectomy or anatomical segmentectomy using a minimization method by balancing the arms with the institution, age (≥ 70 or < 70), sex (male or female), location (right upper, right lower, left upper, or left lower lobes), and histological type (adenocarcinoma or non-adenocarcinoma). The primary endpoint is OS in all randomized patients. Secondary endpoints include relapse-free survival, postoperative respiratory function (at 6 months and 1 year after surgery), proportions of patients with respiratory failure and cerebrovascular disease, cumulative incidence of death from other diseases, cumulative incidence of local recurrence, proportion of patients who undergo segmentectomy, number of resected segments, operative time, blood loss, and adverse events. We plan to enroll 520 patients from 64 institutions over a period of 5 years. Enrollment began in January 2024. As of November 2025, 319 patients have been enrolled. This trial is registered with the UMIN Clinical Trials Registry (UMIN000052064). Clinical trial information: UMIN000052064.