ABLATION OF OLIGOMETASTASIS CANCER WITH STEREOTACTIC ABLATIVE BODY RADIOTHERAPY EXPLOITING THE STEPWISE THEORY OF METASTASIS: A RETROSPECTIVE REVIEW OF A SINGLE INSTITUTION SERIES

Background: Arguably, general anaesthetic was one of the greatest discoveries in the fight against cancer. Yet, many patients are not well enough to undergo a general anaesthetic. Stereotactic ablative body radiotherapy (SABR) is a modern form of radiotherapy whereby lung tumours can be ablated without surgery. For a cancer to metastasise, it needs to detach from the primary tumour, invade blood or lymph, and survive in the circulation until it is embedded in a new site, then re-establish a new blood supply and colony. Multiple mutations are required for a cell to be able to complete all tasks. In theory, ablating the new colony may delay further metastases. We aimed to review patients treated with SABR in one centre. Methods: We retrospectively reviewed results from our institutional SABR programme of patients treated with a single fraction for one to three oligometastases between 2010 and 2015. The primary outcome was local control. Secondary outcomes were freedom from widespread disease (defined as distant recurrence not amenable to surgery or further SABR) and toxicity from treatment scored using the Common Toxicity Criteria version 4.0. Findings: In total 186 treatments were delivered in 132 patients. The two most common target sites were lung (51%) and bone (40%). The most common primary malignancy was genitourinary (n=46). Local control at 1 year was 90% (95% CI 85–95) and at 2 years was 84% (95% CI 77–91). Freedom from widespread disease was 75% (95% CI 67–83) at 1 year and 52% (95% CI 42–63) at 2 years. Compression fracture of the lumbar vertebra was the only grade 3 or higher treatment-related toxicity. Interpretation: This study describes the outcomes of SABR to ablate secondary oligometastases in the lung and bone. Our findings prove that this method is safe and very effective. Funding: None. Conflicts of interest: We declare that we have no conflicts of interest.