Omission of Prophylactic Cranial Irradiation for Limited Stage Small Cell Lung Cancer

• Published in: International journal of radiation oncology, biology, physics Vol. 120; no. 2; p. e54
• Main Authors: Parker, S.M., Videtic, G.M., Weller, M.A., Mastroianni, A., Rajan, S., Yu, N., Stephans, K.L.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-10-2024
• ISSN: 0360-3016
• DOI: 10.1016/j.ijrobp.2024.07.1897

Prophylactic cranial irradiation (PCI) remains the standard of care for most limited stage small cell lung cancer (LS-SCLC) patients that respond well to chemoradiation (CRT). Early trials demonstrated efficacy with this approach but is unclear if results are transferable to the modern era where magnetic resonance imaging (MRI) and positron emission tomography (PET) are readily available.
This retrospective review included all patients with LS-SCLC treated at a single institution from 2013-2023 with definitive CRT followed by omission of PCI. Patients with extensive stage disease, inadequate baseline systemic/intracranial staging, or progression within the first 3 months following treatment completion were excluded. All patients had biopsy confirmed SCLC, received at least 3 cycles of chemotherapy, and received definitive intent RT. Intracranial recurrence free survival (IRFS) was defined as time until development of brain metastasis on imaging (CT or MRI) or symptomatic intracranial progression. Overall survival (OS) and extracranial recurrence free survival (ERFS) were also recorded. Kaplan-Meier method was used for survival analysis.
Fifty-four patients with a median age of 71 (range, 50 – 91) and median baseline KPS of 90 (range, 60 – 100) met inclusion criteria. Median follow up was 12.9 months (IQR, 8.1 – 36.9). All patients underwent baseline intracranial staging with MRI (87%) or CT with contrast (13%) and 98% of patients received PET for systemic staging. Most patients had stage III disease (74%) although stage I (7%) and stage II (19%) were also represented. Six patients (11%) had node negative disease and 4 of those patients (7%) underwent SBRT followed by adjuvant chemotherapy. All other patients underwent definitive concurrent (85%) or sequential (8%) CRT. Patients completed a median 4 cycles (range, 3-6) of platinum-based chemotherapy. Multiple thoracic radiation fractionations were prescribed with 40 Gy/15 fx (44%) as the most common regimen. PCI was omitted primarily due to patient preference (87%) or poor performance status (7%). Intracranial recurrence occurred in 18 patients overall (33%) with 1-year and 2-year intracranial RFS of 65.5% and 62.3% respectively. Among intracranial recurrences, 50% presented as a single lesion and 89% underwent salvage therapy. Extracranial recurrence occurred in 21 patients overall (39%) with 1 and 2-year extracranial RFS of 62.2% and 55.9%, respectively. First recurrence was predominately intracranial (45%) and 13% of patients had simultaneous intracranial/extracranial recurrence. OS at 1, 2, and 3 years was 74.5%, 45.9% and 40.5%, respectively.
Although intracranial failure remains high in this modern cohort, the present study demonstrates comparable intracranial failure rates to PCI arm of historic Auperin et al. meta-analysis (~35% at 2 years), further randomized prospective data is warranted.