Effectiveness of irinotecan-containing regimens in second-line treatment of small cell lung cancer

Background and Aim: Small cell lung cancer (SCLC) is highly sensitive to chemotherapy and radiotherapy, but is associated with high proliferation, early metastasis, and poor prognosis. While platinum-based treatments are preferred in first-line treatment, there are many treatment options in second- line treatment and studies are ongoing. Irinotecan is a topoisomerase-I inhibitor and is preferred in second- line treatment of SCLC. In our study, we aimed to evaluate the response to treatment, factors affecting the success of treatment, and survival times achieved with treatment by retrospectively examining patients diagnosed with SCLC and receiving irinotecan in second-line treatment. Method: In our study, the data of 64 patients who were diagnosed with SCLC and received irinotecan- containing chemotherapy regimen as second-line treatment between September 2012 and September 2024 at the Medical Oncology Clinic of Selcuk University Faculty of Medicine were retrospectively analyzed. All statistical analyses of the study were performed using the statistical software language R version 4.2.1. Survival times were estimated using the Kaplan-Meier method and compared using the Log-rank test. The effects of patient characteristics on progression and death were examined using univariate Cox regression and Hazard ratios (HR) were presented with 95% confidence intervals. Results: In our study, 16 patients out of 64 patients diagnosed with SCLC who received irinotecan- containing regimen in second-line treatment were accepted as treatment responders. The treatment response rate was determined as 25% and the objective response rate as 17.2%. The mean overall survival time of the patients after irinotecan treatment was determined as 7.59 months and the mean progression-free survival time as 3.82 months. The mean progression-free survival time of patients over 65 years of age was determined as longer than that of patients under 65 years of age (p=0.027). The mean progression-free and overall survival times of patients who underwent PCI were determined as longer than that of patients who did not undergo PCI (p=0.001, p<0.001). In first-line treatment, patients who received cisplatin+etoposide regimen had longer median progression-free and overall survival times compared to patients who received carboplatin+etoposide (p=0.040, p=0.007). Patients with good ECOG performance scores had longer median progression-free survival and overall survival times compared to patients with poor ECOG scores (p=0.014, p<0.001). Patients with extensive stage disease had shorter median progression-free survival and overall survival times compared to patients with limited stage disease (p=0.027, p=0.002). Patients with high LDH values at the time of diagnosis had shorter median overall survival times compared to patients with normal LDH values (p=0.041). Conclusion: Irinotecan chemotherapy has a low response rate in the second-line treatment of SCLC and its effect on survival is limited. Being over 65 years of age, having PCI, and cisplatin+etoposide regimen in the first-line treatment were determined as factors that positively affect survival; while poor ECOG performance score, high LDH value, and extensive stage disease were determined as factors that negatively affect survival. Our study is a single-center retrospective study and the number of patients is limited. Prospective studies with larger numbers of patients are needed. Keywords: Small cell lung cancer; Irinotecan; Second-line treatment; Survival