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A study focused on stereotactic ablative radiotherapy (SAbR) as a treatment for primary renal cell carcinoma (RCC) has yielded significant findings. The primary objective of the study was successfully met, demonstrating a 94% local control rate at one year among patients with previously growing tumours. Importantly, this was confirmed through pathologic evidence. However, the study also identified challenges in defining local failure accurately, as two patients experienced radiographic local failure despite histologic response. This highlights the need for additional biopsy sampling post-SAbR. Comparative data from the International Radiosurgery Oncology Consortium for Kidney (IROCK) showed favourable outcomes at two and four years, reinforcing SAbR’s potential as a primary RCC treatment. Notably, a meta-analysis of 383 cases from 26 studies indicated a 97% local control rate at a median 28-month follow-up, with reduced failures in cases using single-fraction SAbR. SAbR demonstrated versatility by effectively treating tumours regardless of their location within the kidney, in contrast to limitations associated with other ablative techniques like radiofrequency ablation (RFA) or cryoablation. Large primary tumours, a challenge for minimally invasive management, were also addressed by SAbR, which showed promise in treating tumours larger than 3-4cm. The study highlighted SAbR’s good tolerance, with low-grade toxicities. Although a decline in renal function was observed, it was comparable to declines seen with other treatments like RFA and cryoablation. A notable finding of the study was the identification of cellular senescence in some surviving tumour cells a year after SAbR, an uncommon discovery in clinical trials. These cells exhibited irreversible cell cycle arrest, suggesting that SAbR induced cell death in most tumour cells. The study’s strengths include its prospective phase two design, inclusion of biopsy-confirmed RCC cases, and post-treatment pathology assessments. However, limitations included the small sample size, a single-arm approach, and reliance on data from a single institution. In summary, the study provides promising evidence for SAbR as a viable treatment option for primary RCC, especially in cases where other methods may not be feasible. Further data, including that from ongoing multicentre studies, is needed to validate these findings and better understand the treatment’s mechanisms and long-term effects.

Phase two trial of stereotactic ablative radiotherapy for patients with primary renal cancer.
Hannan R, McLaughlin MF, Pop LM.
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Asif H Ansari

Lewisham and Greenwich NHS Trust.

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