Oligometastatic disease: Adrenal, lymph nodes, bone

Oligometastasis can be defined as an intermediate state between local and extensive metastatic stage, when few metastases are present, treatment of which can extend patients’ lives. Although its presence could be “felt” before, it was not until 1995 that it could be characterized and start an avalanche of trials that culminated, for now, in the landmark SABR-COMET trial. In the trial survival benefit of the stereotactic treatment of oligometastases was accompanied by a nondeniable rate of high-grade toxicity. With the progression of technology and spreading of magnetic resonance-guided linear accelerators the discrepancy between the planned dose and the dose that a radiosensitive movable luminal organ is actually subjected to during the course of the treatment could finally be defined. This extra dose organs at risk receive due to their unpredictable movement could partially explain the toxicity rate seen in some trials, even though all constraints had been respected initially. The true advantage of the system is not the ability to accurately predict the dose and track the target in real time, thus enabling a decrease in treatment margins, but the capability to reverse it to the initial stage by replanning according to the new anatomy. When the stereotactic treatment is not confined to one target but to many, as in the case of oligometastases, the opportunity to change the plan according to changes in anatomy and spare the organs at risk so that they can sustain multiple treatments without toxicity is of paramount importance. In this chapter, we provide a review of the trials done with conventional systems, the survival benefits, and toxicity of the treatment; discuss the data coming from MR-Linac-related preclinical studies and clinical trials; and conclude with a short prediction about the future of oligometastases and treatment with MR-guided adapted stereotactic radiotherapy.