Novel Radiation Therapy Strategies in Oligometastatic Disease: Building Upon a Legacy of Hemibody Irradiation

Summary: There is increasing use of novel radiation therapy in oligometastatic disease and evidence of a survival advantage for treating metastatic prostate cancer with systemic radiation using 223Ra and 177Lu-PMSA-617. The earliest systemic therapy for patients with bone metastases was hemibody irradiation. The technique was abandoned in favor of chemotherapy and systemic radionuclides. However, with the increasing emphasis on multiple-site and systemic treatments, hemibody irradiation may be a useful synergistic treatment. We recently performed an meta-analysis of all published studies on the efficacy and toxicity of hemibody irradiation as a single or synergistic approach. Initial work was recently published in the inaugural issue of CURIE: The Journal of the American College of Radiation Oncology. A Pubmed search was done of hemibody AND radiotherapy and of half-body AND radiation. The papers were reviewed using Scite for papers that referenced or were referenced by these papers to collect further papers. The references of the papers were reviewed for any further references. The papers were reviewed and papers describing the efficacy and/or toxicity of the treatments were selected. The treatment protocols were reviewed and only papers using single fraction treatments to a hemibody field were abstracted. This resulted in 26 primary reports suitable to be analyzed. A single factor proportional meta-analysis was performed. This was done using MetaXL® This analysis is based upon a double arcsine transformation, which is the preferred method over logit transformation. Because of the wide variability and poor definitions of response, a random rather than fixed model was used for the primary analysis. In our expanded analysis, 46 articles that focused on patients with bone metastases from solid tumors were selected. Redundant articles on the same databases and non-single fraction trials were then eliminated. Further reviews of the papers’ references and using Scite_® to obtain papers referring to these references, resulted in 26 primary reports suitable to be analyzed. Per the analysis, 80% (95% confidence interval of 76% to 84%) of patients had a complete or partial pain response with hemibody irradiation. The same proportion of response was found by fixed result analysis and with quality-adjusted analysis. Among those papers that reported complete response rates, on meta-analysis 29% of patients had a complete response (CI 22% to 37%). The treatment initially had significant acute toxicity but as pretreatment medications advanced and more conformal treatment techniques became available, the toxicity was mild. There were no reports on long-term toxicity. Two fractions of hemibody irradiation has a cost of approximately US$6400, whereas a course of 226Ra costs US$180,000 and a course of 177Lu-PMSA-617 costs US$270,000. Further research into novel irradiation with modern techniques is warranted; our upcoming phase II trials for metastatic prostate cancer will be reviewed. Mitchell Finkelstein, n/a (Presenting Author) - Associated Medical Professions; Charles Scarantino, MD (Co-Author) - University of North Carolina; Christopher Pieczonka, MD (Co-Author) - Associated Medical Professionals; Steven Finkelstein, MD, DABR, FACRO (Co-Author) - Associated Medical Professionals; Lawrence Berk, MD (Co-Author) - Tampa Oncology and Proton