Consolidation thoracic radiotherapy after chemoimmunotherapy in ES-SCLC: A multicentric retrospective analysis

The CREST trial established the benefit of consolidative thoracic radiotherapy (TRT) following first line (1L) chemotherapy in extensive-stage small cell lung cancer (ES-SCLC), demonstrating improved 2-year overall survival (OS). However, the role of TRT in the chemoimmunotherapy (CT-IO) era remains unclear, as TRT was excluded from registrational trials.

This retrospective study analysed consecutive patients (pts) with ES-SCLC treated with 1L CT-IO between January 2020 and January 2024 across 4 centres. Pts without radiological progression (PD) at their first post-treatment assessment were included. Intrathoracic recurrence rates, progression-free survival (PFS), and OS were compared between pts who received TRT and those who did not.

336 pts were identified, with 111 (33.0 %) receiving TRT. Pts who received TRT had a lower rate of intrathoracic PD compared to those who did not (40.5 % vs 57.8 %, p = 0.003). Among those with intrathoracic PD despite TRT, only 21 (24.1 %) experienced PD within the radiation field. With a median follow-up of 31.3 months, pts who received TRT showed improved PFS (HR 0.89, p = 0.363) and OS (HR 0.82, p = 0.142), although not statistically significant. Multivariate analysis identified baseline liver metastases (LM) and stable disease after CT-IO as independent predictors of shorter PFS. Subgroup analysis revealed a longer PFS for pts receiving higher TRT doses (≥45 Gy vs <45 Gy) and those without LM.

In this series, TRT following 1 L CT-IO significantly improved intrathoracic control, although it did not translate into significantly better survival outcomes. Prospective trials are warranted to evaluate the impact of TRT on quality of life and survival.