Musculoskeletal abscopal effect: a review of the important imaging findings and their clinical relevance.

The abscopal effect is a rare but important phenomenon in which targeted therapy of the primary tumor, mainly radiation therapy, leads to the regression of malignant cells at distant sites from the primary tumor and outside the field of treatment. Radioembolization is a developing area of interventional oncology, typically involving microscopic radioactive spheres loaded with yttrium-90. The abscopal effect on distant bone metastases has been previously reported in patients following palliative radiotherapy; however, it has also been observed with more targeted radiation treatments, such as yttrium-90, primarily outside the musculoskeletal system. Musculoskeletal radiologists should be familiar with the abscopal effect, as the indications for radiation therapy are on the rise, and recent advancements in immune therapy have resulted in the induction of the abscopal effect. Herein, we present a case of the abscopal effect in musculoskeletal metastatic disease following targeted radioembolization. We also review the literature on the abscopal effect involving metastatic bone lesions resulting from different types of cancer therapy. Finally, we present recent advancements in cancer treatment with the aim of utilizing this effect.