Supplementary Material for: Factors, including clinical trial eligibility, associated with induction of third-line treatment for advanced gastric cancer

Introduction: Third-line chemotherapy has been suggested to improve survival in patients with gastric cancer. This study aimed to identify factors associated with the induction of third-line chemotherapy for advanced gastric cancer, focusing on patient eligibility for clinical trial. Methods: We retrospectively analyzed 335 patients treated for unresectable or recurrent gastric cancer between April 2009 and May 2020. The patients were grouped into those that met the key eligibility criteria for clinical trial (136 patients, 40.6%) and those that did not (199 patients, 59.4%) before receiving first-line chemotherapy. Results: The overall survival (OS) were 16.8 months (95%CI, 14.0–19.6) and 9.3 months (95%CI, 7.8–11.0) in the eligible and ineligible group, respectively. Multivariate analyses to identify the risk factors associated with the induction of third-line chemotherapy revealed ineligibility of clinical trial (OR 1.95; 95%CI 1.15–3.31), number of metastatic sites (OR 1.99; 95%CI 1.23–3.22), low albumin concentration (OR 2.24; 95%CI 1.14–4.38) and a lack of complete or partial response to first-line treatment (OR 1.85; 95%CI 1.05–3.26). Indeed, in responders to first-line treatment for ineligible patients, the median OS was 17.7 months (95%CI, 10.6–27.9), respectively. Conclusions: Treatment outcomes were different for those eligible for clinical trials and those who were not. However, this study suggested that patients who responded to first-line treatment have more favorable prognoses when treated with salvage chemotherapy, even if they were deemed ineligible for clinical trials.