Use of prophylactic cranial irradiation in patients with extensive-stage small cell lung cancer receiving immunotherapy.

Abstract

e19309 Background: Prophylactic cranial irradiation (PCI) use is controversial in extensive-stage small cell lung cancer (ES-SCLC). In addition to lack of survival benefit of PCI compared to close MRI surveillance in a 2017 published trial, the role of PCI is being further challenged in the modern immune-oncology (IO) era. The IMpower133 trial reporting a survival benefit to atezolizumab for ES-SCLC published in 2018 did not require PCI use. Contemporary practice patterns of PCI in relation to immunotherapy are unknown. Methods: We performed a retrospective cohort analysis of patients with ES-SCLC diagnosed between January 1, 2013 to September 31, 2019 from the nationwide Flatiron Health electronic health record-derived de-identified database. First-line chemotherapy (Chemo) was defined as Chemo given alone, while first-line IO therapy was IO alone or combined with chemotherapy as initial systemic therapy. Results: The cohort included 3047 ES-SCLC patients who received first-line Chemo, and 324 patients who received first-line IO. For first-line IO patients, 268 (82.7%) received first-line atezolizumab. The use of first-line IO increased from 1.2% of patients diagnosed in 2013 to 11.3% of patients diagnosed in 2018 (p < 0.001), and 54.5% of patients diagnosed in 2019 (p < 0.001). Overall documented PCI for patients receiving either first-line IO or first-line Chemo decreased from 14.7% in 2013 to 7.0% in 2018-2019 (p < 0.001). For first-line IO patients, 23 (7.1%) had documented PCI over our study period, with 5.3% of patients diagnosed in 2018-2019 having received PCI. In contrast, for first-line Chemo patients, 428 (14.0%) received PCI over our study period, and PCI use significantly decreased from 14.8% in 2013 to 7.9% in 2018-2019 (p = 0.001). In 2018-2019, use of PCI was not significantly different between patients receiving first-line IO compared to first-line Chemo (5.3% vs 7.9%, p = 0.163). Conclusions: The use of first-line IO has significantly increased in ES-SCLC. Overall PCI rates for ES-SCLC patients decreased significantly over the study period, although documented PCI use rates do not differ between patients receiving upfront IO or Chemo in 2018-2019. Further investigation is warranted regarding effectiveness of PCI in the modern IO era.