The treatment of extracranial oligometastases with advanced therapeutic technologies

Stage IV cancer can be better controlled when metastatic lesions are limited in number and site, which is referred to as a state of oligometastasis. Classically, metastatic disease has been treated with systemic therapy and generally without curative intent. However, studies have shown that surgical resection of certain oligometastases can improve survival and even be curative. Recent prospective data suggests that other forms of local therapy such as stereotactic body radiotherapy (SBRT) may be just as effective in inoperable patients. Whereas conventional radiotherapy has been limited to palliation, SBRT uses image-guidance to deliver individual ablative doses of radiation in a precise manner, and it is suggested that it may also illicit an antitumoral immune response not observed with conventional radiotherapy, ultimately targeting oligometastases with curative intent. With higher dose per fraction, the risk of adverse effects is greater. However, SBRT has been fairly well tolerated to this point. In this chapter, we will review the control, survival, toxicity, and baseline characteristics of patients treated by SBRT with oligometastases to the lung, liver, spine, adrenal glands, and multiple sites. While the results are promising, high quality data from prospective randomized trials are needed before the role of SBRT in the management of oligometastases can be better defined.