Evaluating the Oncologic and Safety Outcomes of High-Dose Palliative Radiation Treatment with 30 Grays in Five Fractions

Introduction In select tumor sites, symptom palliation and local control can be improved through delivering higher biological equivalent doses (BED) of radiotherapy. However, not all patients are suitable candidates for stereotactic body radiation therapy (SBRT). The 30 Grays in five fractions (30/5) regimen is a conformal, hypofractionated regimen that offers a higher BED compared to conventional palliative radiotherapy. It adheres to the same organ-at-risk constraints as five-fraction SBRT. The planning and set-up processes are optimized to expedite treatment delivery compared to SBRT. This study aims to assess the oncologic and safety profiles of the 30/5 regimen. Methods Clinical data of patients who received the 30/5 regimen between October 2020 and August 2022 at our institution, the BC Cancer Vancouver Centre, were retrospectively reviewed. Local control (LC), distant metastasis-free survival (DMFS), progression-free survival (PFS), time to change in systemic therapy (CIS), and overall survival (OS) were calculated using the Kaplan-Meier method. Survival distributions between groups were compared using the log-rank test. Univariable and multivariable analyses were performed using Cox regression analysis to identify factors associated with the oncologic outcomes. Results Over 22 months, 77 patients received 92 courses of the 30/5 regimen. The median age was 68 years. The median tumor size treated was 11.4 cm³. The most common treatment locations were lung (34%), lymph nodes (21%), non-spine bone (18%), and spine (15%). At a median follow-up of 13.5 months, 29 deaths were observed. The 12-month LC was 66.1% (95% CI: 55.7-76.5%), and the 12-month DMFS, PFS, CIS, and OS were 35.9% (95% CI: 24.5-47.3%), 33.2% (95% CI: 22.0-44.4%), 59.2% (95% CI: 46.8-71.5%), and 72.5% (95% CI: 62.1-82.9%), respectively. The univariable analysis showed that radiosensitive and smaller tumors had better LC outcomes (p=0.005 and <0.001, respectively). These associations remained significant upon multivariable analysis too (p=0.035 and 0.026, respectively). No grade three or higher toxicity was reported. Conclusion The 30/5 regimen demonstrates good local control and favorable safety profile, particularly for small and radiosensitive tumors. Our findings suggest that 30/5 may be a viable alternative palliative regimen for patients who require high-dose radiotherapy, but are not suitable candidates for SBRT or prolonged interruptions in systemic therapy. In resource-limited settings, its hypofractionated approach may help conserve healthcare resources. Future studies are warranted to prospectively evaluate the impact of dosimetric distribution on oncologic outcomes.