A Contemporary Update on the Role of Stereotactic Body Radiation Therapy (SBRT) for Liver Metastases in the Evolving Landscape of Oligometastatic Disease Management

Metastases to the liver are common, and stereotactic body radiation therapy (SBRT) is a recognized tool for ablation of liver metastases. Colorectal cancers commonly metastasize to the liver, and long-term survival is possible after metastasectomy. However, many patients are not candidates for surgical resection, which opened the door to early studies investigating noninvasive techniques such as liver SBRT. Multiple prospective trials have demonstrated excellent local control with this approach coupled with an excellent safety record. The oligometastatic disease state is now appreciated across many histologies, and treatment of liver metastases as a component of oligometastatic disease management has emerged as a rational and relevant strategy. To this end, recent randomized studies in oligometastatic non-small-cell lung cancer demonstrated improved progression-free survival with consolidative local therapy, and this approach is the topic of ongoing cooperative group studies inclusive of patients with an array of primary histologies. Further, there is a push to explore the role of radiation as a means to enhance the efficacy of immune enabling drugs. Recent prospective data evaluating the safety and response of SBRT with anti-CTLA-4 therapy for patients with lung or liver metastasis demonstrated clinical benefit (out of field immune-related partial response or immune-related stable disease ≥6 months) in about a quarter of enrolled patients. Interestingly, SBRT to liver metastases was found to elicit a greater systemic immune response than SBRT to lung metastases. Classic management paradigms for metastatic disease are rapidly being supplanted by approaches that are improving outcomes for patients previously offered best supportive care or palliation alone. In this article, we will review the established and emerging potential indications for liver SBRT in this new era of oncologic care.