Factors affecting survival and prognosis in extensive stage small cell lung cancer

Although chemotherapy significantly improves the quality of life and prolongs survival in patients with extensive-stage small cell lung cancer (ES-SCLC), relapse is almost inevitable, with only 5% of patients surviving two years after the initial diagnosis. Prophylactic cranial irradiation (PCI) is considered for patients who achieve a complete response, as it has been shown to improve survival rates in this population. Recent studies have also demonstrated that adding PD-L1 inhibitors, such as atezolizumab or durvalumab, to chemotherapy in first-line treatment significantly enhances survival compared to chemotherapy alone. Our study was conducted retrospectively at a single center, including 280 patients with ES-SCLC who began therapy at our institution between July 2009 and February 2023. Patients who underwent thoracic residual radiotherapy (p< 0.001) and PCI (p< 0.001) showed statistically significant improvements in OS. In the first-line treatment group, the median overall survival (OS) for patients receiving cisplatin+etoposide was 12.0 months (10.71 - 13.28), while those treated with carboplatin+etoposide had a median OS of 7.0 months (4.58 - 9.41). For patients receiving carboplatin+etoposide+atezolizumab, the median OS was 35.0 months (21.32 - 48.67), and a statistically significant difference was observed (p< 0.001). In our study, the median OS was 7 months in patients who received ≤ 4 cycles of treatment in the first line and 14 months in patients who received > 4 cycles of treatment. After first-line treatment, the proportion of patients with progression-free survival (PFS) between 0 - 3 months was 21%, and between 3 - 6 months was 24%. PFS was notably worse in those with bone, liver, or brain metastases at diagnosis in the first-line treatment. Multivariate analysis revealed that carboplatin+etoposide+atezolizumab in the first line and cisplatin+etoposide in the second line reduced the risk of both progression and death, while PCI reduced the risk of death. In conclusion, ES-SCLC remains one of the most challenging malignancies, characterized by poor survival rates and short progression-free intervals. Multiple factors influence OS and PFS, some of which are intrinsic to the patient and disease at diagnosis. In contrast, others, such as treatment modalities, the number of treatment cycles, and the application of radiotherapy, can be modified by clinicians.