2001P Consolidative thoracic radiotherapy of extensive-stage small cell lung cancer in the era of chemoimmunotherapy: A retrospective analysis concerning patients from southern Italy

Consolidative thoracic radiotherapy (TR) was commonly used in the management of extensive-stage small cell lung cancers (ES-SCLC) in the past years. Nevertheless, phase III trials concerning first-line chemoimmunotherapy excluded these treatment approach. However, there is a strong biological rational to support the use of radiotherapy, as boost for sustaining anti-tumor immune response. Currently, the benefit of TR after chemoimmunotherapy remains unclear. Herein we include a real-world experience concerning 120 patients with ES-SCLC treated with chemoimmunotherapy combinations. A total of 120 ES-SCLC patients treated with chemoimmunotherapy since 2019 in the South of Italy were retrospective analyzed. After 4 cycles of chemoimmunotherapy, all patients selected for the analysis obtained an adequate response for a subsequent TR. Of the 120 patients included in the analysis, 59 patients underwent TR. Patient characteristics, chemoimmunotherapy schedule, and timing for start TR were assessed. Primary endpoint was safety, secondary endpoint was the efficacy, namely OS and PFS. TR was associated with a good safety profile and with no significant changes in grade ≥3 AEs. In particular, none grade ≥3 AE was reported in the TR group versus two grade 3 AEs in the control group. The median time for start TR after 4 cycles of chemoimmunotherapy was 62 days (range 10-184). TR and fraction range include from 30 Gy (in 10 fractions) up to definitive dose in selected patients. TR was associated with a significantly longer PFS than systemic therapy alone (1-year PFS 55% vs. 1-year PFS 28.1%, p=< 0.0001) and was also associated with a trend toward longer PS (1-year OS 79,4% vs. 1-year OS 57,5%, p= 0.11). Multi-center experience from South of Italy confirms a general confidence in using TR as consolidative strategy after chemoimmunotherapy based on clinical multidisciplinary decision. With the limit of a retrospective analysis, these preliminary results support the feasibility of this approach and encourage a prospective evaluation.