Analysis of retreatment after radiotherapy for bone metastasis at a safety net hospital.

Abstract

223 Background: The effectiveness of single fraction radiotherapy in the treatment of bone metastasis is firmly established by multiple prospective randomized controlled trials. These trials have also indicated a retreatment rate that is significantly higher for patients treated with single fraction radiotherapy. The reason for this is unclear. The prior studies have confirmed that there are no differences in any objective or subjective measure of response or durability of response. One proposed explanation may be a conscious or subconscious impact of practice based workload accounting for adopting a single fraction treatment strategy that may lead to excess retreatment prescription. In other words, does a decrease in workload accounting due to single fraction treatment lead to an increase in retreatment rates? Our large safety net teaching hospital follows a practice model where department funding is independent of workload accounting. We retrospectively reviewed our data on the radiotherapy of bone metastasis to see if this practice model had any impact on our retreatment rates. Methods: Between October 2012 and June 2017, 225 patients received treatment for 385 target lesions. All referred patients’ entire radiotherapy history was included whether or not it occurred during the target period. 196 target lesions received single fraction treatment and 189 received multiple fractions. 27 target lesions were retreated once and a single target lesion was retreated twice. Results: Target lesions treated with a single fraction resulted in a retreatment rate of 7.7% while multiple fraction treatment resulted in a retreatment rate of 6.4%. This difference was not statistically significant by Chi-Square analysis. Conclusions: Our retrospective analysis confirms no difference in retreatment rates between single and multi-fraction treatment. The retreatment rate is in agreement with the published response rate and introduces a possible explanation for the discordant rates observed in the published literature. Further analysis involving multiple practice models would help further explore these findings.