S-1 Maintenance Therapy in Extensive Stage Small-Cell Lung Cancer—A Randomized Clinical Study

Small-cell lung cancer (SCLC) is a recalcitrant cancer for its dismal prognosis although extensive research had been done. Four to 6 cycles platinum-based chemotherapy is the mainstay treatment for the extensive-stage disease; but the role of maintenance treatment is not fully understood. This is a phase 2, open-label study. Patients with extensive-stage SCLC reaching an objective response or stable disease (SD) after induction chemotherapy were randomly assigned (1:1) with a minimization procedure. One group received oral S-1 and the other group received placebo as maintenance treatment until disease progression or unacceptable toxicities. The primary end point of this study was progression-free survival (PFS), and the secondary end points were overall survival (OS), response rates, and toxicities. This study was based on earlier work, the preliminary results was reported on 2019 ASCO annual meeting. A total of 89 patients were enrolled, of whom 45 received S-1 maintenance therapy and 44 received placebo. The median PFS and OS were 6.35 months and 10.82 months in the S-1 group, as compared to 5.98 months and 10.09 months in the placebo group. The PFS was 7.2 months and 5.3 months, and OS was 12.9 months and 10.9 months in patients with an objective response compared to in patients with SD after induction chemotherapy, respectively. S-1 maintenance therapy did not prolong PFS or OS in patients with extensive-stage SCLC; tumor regression rate was the prognostic factor of PFS or OS. Further research with novel agents in the maintenance setting is warranted.