2550 - Hyperfractionated Thoracic Radiotherapy in Extensive-Stage Small Cell Lung Cancer: A Retrospective Study

Purpose/Objective(s): The role of hyperfractionated thoracic radiotherapy in extensive-stage small-cell lung cancer (ES-SCLC) remains controversial. This study aimed to evaluate the efficacy and safety of hyperfractionated versus conventionally fractionated thoracic radiotherapy in ES-SCLC.

Materials/Methods: This retrospective study included 105 patients who received first-line chemotherapy between 2020 and 2024 and were assessed as having stable disease (SD) or partial response (PR) according to RECIST 1.1. These patients subsequently received consolidative thoracic radiotherapy. The cohort was divided into two groups: 61 patients in the hyperfractionation group (1.5 Gy per fraction × 30 fractions, twice daily) and 44 patients in the conventional fractionation group (2 Gy per fraction × 30 fractions). The primary endpoints were overall survival (OS), progression-free survival (PFS), and local recurrence-free survival (LRFS). Secondary endpoints included adverse events (AEs). Statistical analyses were performed using SPSS software, and a two-sided P-value of 0.05 was considered significant.

Results: There were no significant differences in OS between the hyperfractionated and conventional groups (18.2 months vs. 14.1 months, HR = 0.863, 95% CI = 0.461-1.624, P = 0.644). Similarly, no significant differences were found in PFS (6.9 months vs. 4.8 months, HR = 0.937, 95% CI = 0.583-1.507, P = 0.788) or LRFS (9.4 months vs. 7.4 months, HR = 0.993, 95% CI = 0.642-1.537, P = 0.976). Subgroup analysis showed that initiating thoracic radiotherapy within =4 cycles of chemotherapy significantly prolonged PFS compared to starting after > 4 cycles (6.9 months vs. 4.3 months, HR = 0.569, 95% CI = 0.358-0.905, P = 0.644). In terms of AEs, while no significant difference was observed in the overall incidence, the hyperfractionated group exhibited a significantly lower risk of = grade 3 radiation pneumonitis compared to the conventional group (P = 0.004). Logistic regression analysis confirmed that hyperfractionation was the only significant protective factor against the occurrence of = grade 3 radiation pneumonitis (OR = 0.072, 95% CI = 0.008-0.681, P = 0.022).

Conclusion: Hyperfractionated thoracic radiotherapy for primary chest lesions in extensive-stage SCLC showed similar efficacy to conventional fractionation in terms of OS, PFS, and LRFS. However, hyperfractionated radiotherapy was associated with a significantly lower risk of =grade 3 radiation pneumonitis. These findings support that hyperfractionated thoracic radiotherapy might be a safe and effective treatment option in ES-SCLC