Utilization of Radiation Fractionation for Bone Metastases at the End of Life in the Era of SBRT: A Large Single Institution Longitudinal Experience

Abstract

Radiation therapy (RT) is effective in managing painful bone metastases. Multiple randomized trials have demonstrated that single fraction radiotherapy is not inferior to multi-fraction treatments for symptom relief. ASTRO treatment guidelines recommend a single 8Gy fraction to bone metastases for patients with limited life expectancy. We sought to evaluate the use of RT fractionation and the ability of physicians to predict short life expectancy as reflected by their choice of treatment regimen. All patients who received RT for bone metastases (BM) between 2016-2018 at a single institution were identified, as was the subset of patients who died within 30 days after receiving RT for BM. To understand longitudinal trends, treatments were binned into 6-month intervals by date of final radiation treatment. RT fractions were grouped by 8Gy in a single fraction (8Gy x 1), 30Gy in 10 fractions (3Gy x 10), other conventional RT fractionations, and stereotactic body RT (SBRT). To determine the presence of an increasing or decreasing trend, proportions were compared over time using a Chi-square test. The overall change in the use of an RT fractionation was also assessed between the beginning and end of the study period using a 2-sample proportion test. From 2016-2018, 3,056 patients underwent 6,811 palliative RT courses for BM, and 480 patients (16%) died within 30 days of their last treatment. The total number of treatments for BM increased by 27% during the study period. Among all BM treated, use of SBRT had an increasing trend (p<0.001) with a difference in use over the study period (37% to 48%, p<0.001), while 3Gy x10 has a decreasing trend (p<0.001) with a change in use (25% to 11%, p <0.001) and 8Gy x1 has remained stable over time (p=0.4) with no significant difference in use (4.5% to 4.8%, p= 0.8). The trends were mirrored among patients dying within 30 days of RT; SBRT with an increasing trend (p=0.039) and change in use (18% to 33% p= 0.03), 3Gy x10 with a decreasing trend (p<0.001) and change in use (32% to 7%, p<0.001), while the number of patients treated with 8Gyx1 remained stable (p=0.4) with no significant difference in use (9% to 17%, p= 0.2). A 33% relative reduction (9.5% to 6.6%) in death within 30 days of RT was observed. Our study demonstrates an increase in patients undergoing RT for BM over time while the overall rate of death within 30 days of RT has decreased, most likely due to more patients getting treated earlier in their disease course. Of the patients dying within 30 days of RT for bone metastases, a significant decline in the use of 3Gy x10 was observed during the study period, but the use of 8Gy x1 did not increase, potentially related to the increase in use of SBRT. Our results warrant further investigation into algorithms predicting short life expectancy and implementation strategies to increase use 8Gy x1 at the end of life.