Purpose: We aimed to investigate whether induction chemotherapy with less than four courses is as effective as induction chemotherapy with more than four courses in non-small cell lung cancer (NSCLC) patients receiving chemoimmunotherapy. Methods: We retrospectively enrolled 249 patients with NSCLC who received chemoimmunotherapy at 12 centers in Japan between January and December 2019. The patient group that completed less than four courses owing to adverse events (AEs), and received subsequent maintenance therapy was compared to the group that received at least four courses of induction chemotherapy followed by maintenance therapy. Results: On univariate and multivariate analyses, the patient group that transitioned to maintenance therapy after completing less than four courses of induction chemotherapy had significantly shorter progression-free survival (PFS) than those who completed at least four courses (hazard ratio [HR] 2.15, 95% confidence interval: 1.38–3.37, p < 0.001 and HR 2.32, 95% confidence interval: 1.40–3.84, p = 0.001, respectively). There was no obvious difference in PFS between the group in which induction chemotherapy ended in two or three courses leading to partial or complete response, and the group that continued at least four courses of induction chemotherapy (log-rank test p = 0.53). Conclusion: Treatment efficacy may be maintained if induction chemotherapy is completed in less than four courses owing to development of AEs, and is administered for more than two courses with partial or complete response; efficacy is maintained even on transitioning to maintenance therapy.
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