Background: Recent trials have demonstrated improved overall survival (OS) with the addition of immunotherapy to platinum/etoposide chemotherapy in ES-SCLC. However, in these studies thoracic radiotherapy (TRT) was excluded, and its role in the current treatment paradigm is unclear.

Aim: To examine treatment patterns and outcomes for ES-SCLC treated with chemoimmunotherapy, with a focus on TRT utilisation.

Methods: A retrospective audit of patients with ES-SCLC diagnosed within Sunshine Coast and Metro North Hospital and Health Services from March 2020 to March 2022 was undertaken. Demographics, systemic therapy, radiation data, toxicity and outcomes were recorded. Descriptive statistics and Kaplan Meier survival analysis were utilised.

Results: A total of 50 patients treated with chemo-immunotherapy were identified across three sites (median age 63 years; 56% female). Seven patients (14%) received TRT with doses ranging from 30 to 50 Gy. The majority had stage IIIC (n = 2) or IVA (n = 2) disease at baseline, and only three had extra-thoracic metastases. Indications for TRT included: persistent bulky thoracic disease following chemo-immunotherapy (n = 3); responding thoracic disease without extra-thoracic metastases (n = 2); concurrent TRT due to symptomatic thoracic disease (n = 1) and persistent low volume thoracic disease with low volume extra-thoracic burden (n = 1). In the overall population, progression-free survival at 6-months was 42% (95% CI:30%–58%). Median OS was 9.24 months, and six and 12-month OS were 78% and 36% (95% CI: 25%–53%) respectively. Median OS in those receiving TRT was 15.3 months. TRT was generally well tolerated with only one patient experiencing grade ≥3 toxicity (pneumonitis).

Conclusions: TRT utilisation occurred in a minority of patients undergoing chemo-immunotherapy in ES-SCLC. As expected, TRT when utilised, was in those with minimal or no extra-thoracic disease and/or bulky residual thoracic disease following chemotherapy. TRT appeared to be well tolerated in these select patients. The role of TRT has yet to be determined in ES-SCLC treated with chemo-immunotherapy.