Phase II study of S-1 in patients (pts) with previously treated Invasive thymoma (IT) and thymic carcinoma (TC): North Japan Lung Cancer Study Group Trial 1203.

Abstract

8564 Background: Invasive thymoma and thymic carcinoma are rare epithelial neoplasms arise in the anterior mediastinum. Platinum-based chemotherapies are widely used for the first-line treatment for unresectable IT and TC. Although no standard treatment has been established for previously treated IT and TC, S-1 has demonstrated promising efficacy in some retrospective studies. Thus we conducted the first prospective multicenter phase II trial to evaluate the efficacy of S-1 for previously treated pts with advanced IT and TC. Methods: Eligible pts were aged 20 years or older with: advanced IT or TC not feasible to potentially curative treatments; disease progression after at least one regimen of platinum-based chemotherapy; Eastern Cooperative Oncology Group performance status 0-2; adequate organ function; written informed consent. Pts received S-1 orally, at a dose based on body surface area for 2 weeks in 3 weeks cycle until tumor progression or unacceptable toxicities. The primary endpoint was overall response rate (ORR) and secondary endpoints were progression-free survival (PFS), overall survival (OS), and toxicity profile. Assuming that ORR of 25% in eligible pts would indicate potential usefulness while ORR of 10% would be the lower limit of interest, with alpha = 0.05 and beta = 0.2 according to a Simon’s two-stage design, the estimated accrual was 40 pts. Results: Between June 2012 and August 2018, 40 pts were enrolled and all pts were eligible (IT, n = 20; TC, n = 20). Median age was 64.5 years (range, 40-82), 75% (30/40) were male. Median treatment cycle was 5.5 (range, 1-82). ORR was 17.5% (95% CI: 7.3-32.8; IT, 10%, TC, 25%), and disease control rate was 85% (IT, 95%, TC, 75%). With a median follow-up of 51.9 months, median PFS was 7.0 months (IT, 11.3 months; TC, 5.4 months), and median OS was 40.3 months (IT, 58.5 months; TC, 22.7 months). The major grade 3-4 toxicities were anorexia (10%) and pneumonitis (5%). No treatment-related death was observed. Conclusions: Although the primary endpoint was unmet, S-1 monotherapy showed the moderate effects and could be available option especially for previously treated advanced TC. Clinical trial information: 000008174.