Stereotactic ablative body radiotherapy for primary kidney cancer: what have we learned from prospective trials and what does the future hold?

10.2217/fon.16.6 © 2016 Future Medicine Ltd In the USA, kidney cancers are currently the 7th and 10th most commonly diagnosed cancers in men and women respectively, with 61,560 new cases expected in 2015, the majority of which will be primary renal cell carcinoma (RCC). Kidney cancer was the 9th most commonly diagnosed cancer in Australia in 2014. Surgical excision is the gold standard for the treatment of primary RCC in fit patients with adequate renal function, with thermoablative techniques such as cryoablation and radiofrequency ablation (RFA) often being utilized in patients who are medically inoperable. More recently, stereotactic ablative body radiotherapy (SABR) is emerging as a promising new weapon in the a rmamentarium against primary RCC. Evidence for efficacy & safety of SABR for primary RCC While RCC is typically considered resistant to radiation delivered using conventional fractionation schedules (1.8–2 Gy per fraction), preclinical evidence indicates that RCC may not be resistant to ablative doses of radiation. Preclinical evidence from Ning et al. suggests that the cell survival curves of two of the most common human RCC cell lines (Caki-1 and A498) exhibited a low α/β ratio (and thus may be sensitive to higher dose per fraction radiation) [1]. The sensitivity of RCC to ablative doses of radiation was suggested by Walsh et al. using a nude mouse model with an implanted human RCC cell line [2]. Biological mechanisms COMMENTARY