Beyond the Knife in Renal Cell Carcinoma: A Systematic Review—To Ablate or Not to Ablate?

SIMPLE SUMMARY: Over the last 10 years, there has been a vast increase in the use of targeted and immunotherapy drugs in the management of advanced kidney cancer. As patients are living longer with cancer that has spread, the natural history has altered, with problems of poor tumour control in one or a few areas only. Local surgical removal of the tumour(s) frequently cannot be applied due to technical challenges or patient factors. Thermal ablation or stereotactic body radiotherapy (SBRT) may be utilised. Thermal ablation is a minimally invasive treatment where heat is generated and passed via a probe into the tumour to cause cancer cell death. SBRT is a non-invasive treatment where high radiobiological doses of radiation are precisely delivered in one, or a few, treatments to kill cancer cells. This systematic review aims to evaluate the existing evidence for these treatments to help improve personalised care for individual patients. ABSTRACT: Intensified systemic therapy in metastatic renal cell carcinoma (mRCC) has led to improved patient outcomes. Patients commonly require local control of one or a few metastases. The aim was to evaluate metastasis-directed ablative therapies in extracranial mRCC. Two databases and one registry were searched, using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) approach, for all prospective and matched-pair case–control mRCC studies of radiofrequency ablation (RFA), cryotherapy, microwave ablation (MWA), and stereotactic body radiotherapy (SBRT). Eighteen studies were identified. Fourteen investigated SBRT in 424 patients. Four thermal ablation studies were identified: two cryotherapy (56 patients) and two RFA studies (90 patients). The median participant number was 30 (range 12–69). The combined median follow-up was 17.3 months (range 8–52). Four SBRT studies reported local control (LC) at 12 months, median 84.4% (range 82.5–93). Seven studies (six SBRT and one cryotherapy) reported an LC rate of median 87% (79–100%). Median overall survival (OS) was reported in eight studies (five SBRT, two cryotherapy, and one RFA) with a median of 22.7 months (range 6.7–not reached). Median progression-free survival was reported in seven studies (five SBRT, one cryotherapy, and one RFA); the median was 9.3 months (range 3.0–22.7 months). Grade ≥ 3 toxicity ranged from 1.7% to 10%. SBRT has excellent local control outcomes and acceptable toxicity. Only four eligible thermal ablative studies were identified and could not be compared with SBRT. Translationally rich definitive studies are warranted.