Examining the Efficacy and Safety Profile of Palliative Radiotherapy Using 30 Gy in 5 Fractions

Abstract

Higher biological equivalent doses of radiotherapy (RT) can improve symptom palliation and local control in select tumor sites. However, not all patients meet criteria for treatment with stereotactic ablative radiotherapy (SABR). Furthermore, SABR is a resource intensive technique which may limit its use in many centers. The 30 Gray in 5 fractions regimen (30/5) stems from a modification of 5-fraction SABR regimens. It is a conformal, homogenous hypo-fractionated regimen that delivers higher dose than conventional palliative RT while still respecting the normal tissue constraints for 5-fraction SABR. It uses streamlined contouring and planning with less stringent requirements for immobilization and image guidance, compared to what is required for SABR. This study evaluates the clinical outcomes of patients receiving 30/5. A single institution retrospective review of clinical and treatment data was performed for patients who received 30/5 from October 2020 to August 2022. Local control (LC) was calculated for all treatment courses. Distant metastasis-free survival (DMFS), progression-free survival (PFS), and overall survival (OS) were calculated for all patients. Survival analyses were analyzed by the Kaplan-Meier method and curves compared by log-rank test. Univariate and multivariate analyses were performed using cox-regression analysis. A total of 77 patients and 92 courses of 30/5 were available for analysis. The most common primary tumor was lung (44%), followed by gastrointestinal (GI; 20%), breast (10%), and genitourinary (10%). The median age of patients was 64 years (range: 37-93). The median tumor size treated was 11.4 cm^3 (range: 0.3 - 210.9 cm^3). Treatment sites included lung (31%), lymph nodes (22%), non-spine bone (20%), and spine (15%). At median follow-up of 10.1 months (mo), 25 deaths occurred. Median LC after receiving 30/5 was 18.5 mo (95% CI: 15.7-21.3 mo), median DMFS was 6.6 months (95% CI: 4.6-8.6 mo), median PFS was 6.4 mo (95% CI: 4.9-8.0 mo), and median OS was 18.1 mo (95% CI: 13.1-23.1 mo). Median time to initiating, restarting, or changing systemic therapy was 12.8 mo (95% CI: 7.6-18.0 mo). Radiosensitive (lung, prostate, breast, gynecological, and head/neck) tumors had better LC than radioresistant (GI, renal cell, sarcoma, melanoma) tumors (median 20.9 vs 12.1 mo, p < 0.02). Six grade 2 toxicities occurred (6.5% of all treatments). No grade 3 or higher toxicities occurred. The 30/5 regimen is a safe, well-tolerated, and resource efficient regimen with effective local control. This may serve as a practical alternative for patients who require palliative RT but not optimal candidates for SABR. As expected, radiosensitive tumors had better local control than radioresistant tumors. Future research can further explore the safety, efficacy, and indications of 30/5 as a palliative RT option.