The Management of Small Renal Tumours by Ablative Therapies

Abstract

Renal cell carcinoma (RCC) was the 9th commonest malignancy in Europe in 2008 [1] with an estimated 88400 new cases and 39300 deaths [2] making it the most lethal urological malignancy. Over the last 2 decades there has been a significant increase in the incidence of small renal masses (SRMs) at diagnosis often as an incidental finding as a result of abdominal imaging for the investigation of pain or other abdominal symptoms [3]. This has resulted in a stage migration to smaller and lower stage lesions in asymptomatic patients [4]. Many of these SRMs are slow growing and of low malignant potential although the precise natural history remains unclear [5]. The rate of radiographic growth in most series which have followed renal masses usually for 3 years is between 0 and 0.86 cm/yr with a metaanalysis by Chawla et al reporting an overall median growth rate of 0.28cm/year [6]. Some tumours however will behave more aggressively and at present it is not possible to determine in advance which tumours these are. Nephron sparing surgery (NSS) represents the gold standard for the small renal mass and radical surgery for the T2 and larger tumours. Although laparoscopic nephron sparing surgery has been demonstrated to be both feasible and oncologically equivalent to open nephron sparing surgery it is widely acknowledged to be technically demanding with a steep learning curve and associated morbidity. This particularly relates to keeping warm ischaemia time to a minimum. In one of the largest series Gill et al reported a median surgical time of 3 hours and a median warm ischemia time of 27.8 minutes [7]. Although robotically assisted partial nephrectomy is gaining acceptance, active surveillance and minimally invasive alternatives including ablative techniques have emerged as alternatives to nephron sparing surgery or radical nephrectomy. The main ablative techniques in clinical use are cryotherapy and radiofrequency ablation. Cryotherapy is more frequently applied laparoscopically and radiofrequency ablation percutaneously. In some institutions including the Cleveland Clinic selected tumours are preferentially treated with minimally ablative techniques rather than with partial nephrectomy [8]. In addition other emerging techniques that have been described include High Intensity Focused Ultrasound, Microwave thermotherapy, Interstitial Laser ablation and CyberKnife. Whilst there is increasing evidence in support of radiofrequency ablation