The method of patient selection is shown in Fig. 1. A total of 53 NSCLC patients met the selection criteria, and this population was defined as the FAS.
The patient characteristics are shown in Table 1. Of the total 53 patients, 26 patients (49.0%) were < 70 years of age. Age, PS, smoking history, staging, and EGFR gene mutation status were similar with the historical control. There were no patients with ALK fusion gene. Forty-six patients had adenocarcinoma (88.7%) and no patients had squamous cell carcinoma. Regarding treatment delivery, 31 patients (58.5%) received the standard S-1 regimen (4 weeks administration followed by 2 weeks of rest, every 6 weeks) and 18 patients (34.0%) received the modified S-1 regimen (2 weeks administration followed by 1 week of rest, every 3 weeks) for the first S-1 cycle. Twenty-four patients received 5 or more PEM rounds of administration. The median period between last PEM administration and first S-1 administration was 118 days (range: 11–625 days). No immune check point inhibitors (ICIs) were administered between PEM and S-1.
The treatment efficacy of S-1 is shown in Table 2. ORR was 1.9% (95% confidential interval [CI]: 0.00-10.1%) and DCR was 41.5% (95% CI: 28.1–55.9%). Median TTF, PFS and OS were Collating preplanned criteria, the treatment effect of S-1 after PEM, might be less than that of the no prior PEM treatment population. Moreover, in the historical control, especially the adenocarcinoma subset, ORR was 15.8% (95% CI: 3.3–39.8%) and DCR was 57.8% (95% CI: 33.5–79.7%).
Median TTF, PFS, and OS in this study were 65 days, 84 days, and 385 days, respectively (Fig. 2). In the adenocarcinoma subset of historical control, median PFS and OS were 4.2 months and 15.7 months, respectively (TTF was not shown). Compared with historical control, PFS and OS in this study tended to be worse.
To search for the predictive factor of S-1 effect after PEM containing treatment, differential analysis was used about two factors. One was the number of PEM administration and the other was the period between last PEM administration and first S-1 administration. ORR was too low to analyze, TTF and PFS were used as a surrogate of efficacy. Between-group differences in TTF and PFS were assessed using the stratified log-rank test. Both of two factors could not predict the efficacy of S-1 after PEM treatment (Fig. 3, Fig. 4). However, the longer period between last PEM and first S-1 group tended to longer PFS and TTF.