Irinotecan monotherapy as third- or further-line treatment for patients with small cell lung cancer

Background: Small cell lung cancer (SCLC) is a very aggressive cancer and recurrence is inevitable. Treatment of recurrent disease is important for improving the prognosis of patients with SCLC. Methods: We conducted a retrospective observational study to investigate the efficacy and safety of irinotecan monotherapy as third- or further-line treatment in patients with SCLC. Results: Data of 15 patients who had received irinotecan monotherapy as third- or further-line treatment between 2004 and 2019 were analyzed. The median progression-free survival duration (95% confidence interval) from the initiation of treatment with irinotecan was 2.7 (1.4-3.8) months, and the median overall survival duration (95% confidence interval) from the initiation of irinotecan treatment was 10.0 (3.9-12.9) months. Partial response, stable disease or non-complete response/non-progressive disease, and progressive disease were observed in 1, 6, and 8 patients, respectively. Adverse events > grade 3 in severity were observed in 2/2 (100%) patients who were homozygous for UGT1A1 mutation, 2/3 (66.7%) patients who were heterozygous for UGT1A1 mutation, 4/6 (66.7%) patients who had wild-type UGT1A1, and 2/4 (50.0%) patients in whom the UGT1A1 mutation status was unknown. Conclusion: Our results suggest that irinotecan monotherapy can be a useful alternative treatment option in the third-line setting for patients with SCLC.