Definitive radiotherapy practices for small-cell lung cancer in Japan: a national survey (JROSG 23-3)

This survey examined the real-world practice of radiotherapy for small-cell lung cancer (SCLC) in Japan, focusing on treatment strategies for limited-disease SCLC (LD-SCLC) and extensive-disease SCLC (ED-SCLC). This study aimed to identify inter-institutional differences, optimize treatment strategies and explore opportunities for standardization. A questionnaire was distributed to members of the Japanese Radiation Oncology Study Group, and responses were collected from 15 December 2023 to 14 March 2024. Responses to 11 questions specifically related to SCLC treatment strategies were analyzed. Among the 112 institutions, 38.3% did not set an upper age limit for concurrent chemoradiotherapy in LD-SCLC, whereas 31.3% set the limit at 80 years. The most commonly used chemotherapy regimen was cisplatin plus etoposide (79.5%), and the predominant radiotherapy fractionation schedule was twice-daily 45 Gy in 30 fractions (97.3%). Elective nodal irradiation (ENI) was ommited in 30.4% of institutions, while 17.9% reported performing ENI in all cases. Intensity-modulated radiation therapy (IMRT) was introduced in 71.4% of institutions, with D50% as the most frequently used dose-prescription method (47.5%). After achieving complete response, 16.1% of institutions routinely perform prophylactic cranial irradiation (PCI) in all patients. Hippocampus-sparing PCI was not widely used at the time of the survey (13.3%). In conclusion, this Japanese nationwide survey highlighted the SCLC treatment patterns and differences compared with non-small lung cancer (NSCLC). ENI omissions and IMRT have become increasingly adopted for SCLC, whereas clinical target volume margin definitions show some variation compared with NSCLC. Regular surveys are essential to monitor the evolution of treatment strategies.