From the Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto, Toronto, Ontario, Canada
Author's disclosure of potential conflicts of interest is found at the end of this article.
Address reprint requests to Laura A. Dawson, MD, Associate Professor, Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto, 610 University Avenue, Toronto, Ontario, M5G 2M9 Canada; e-mail: laura.dawson{at}rmp.uhn.on.ca
Overview: Although radiation therapy is an effective anticancer intervention on its own or combined with other treatment modalities for many malignancies, its role in liver metastases is less clearly defined. This is partially because of the low, whole-liver tolerance to radiation and challenges in safely delivering high doses of radiation therapy to liver metastases. Advanced radiation therapy planning and delivery technologies are now widely available — including computerized tomography-based conformal radiation planning, breathing motion management strategies, and image guidance at the time of radiation delivery — making it possible for tumoricidal doses of radiation therapy to be safely delivered to focal, unresectable liver metastases, thus sparing doses to the majority of the uninvolved liver. Potent doses of radiation therapy delivered in fewer fractions than conventional radiation therapy, with very high accuracy and precision (referred to as stereotactic body radiation therapy), is an efficient strategy to deliver radiation therapy, most suitable for liver metastases less than 6 cm in maximum diameter. Clinical experience in radiation therapy for unresectable liver metastases is growing and demonstrating excellent local control rates. The optimal integration of radiation therapy with other treatment modalities is unknown, but worthy of future research efforts.
