ASCO GU 2017: Intermediate-term outcomes from the DISSRM registry: A prospective analysis of active surveillance in patients with small renal masses.

Orlando, Florida USA (UroToday.com) As is now well known, the increased incidence of small renal masses (SRMs) from higher utilization of cross-sectional abdominal imaging has led to increasing interest in minimally-invasive management of these tumors. Dr. Thomas Atwell from Mayo Clinic presented the best evidence for the role for thermal ablation in the management of SRMs. Ablation comes in two major forms: Heat ablation via radio frequency ablation (RFA) or microwave ablation (MWA), and cold ablation (cryoablation). Dr. Atwell warns that although the literature tends to group “ablation” into one bucket, they are really different techniques and should be studied in their respective categories.

RFA is a successful technique under the appropriate circumstances. Data demonstrate a 88-98% RFS, 75-95% DFS, and 80-100% CSS. RFA is good for small tumors, with 97-100% successful treatments for tumors <=3cm, whereas treatment for tumors >3cm is only successful 60-86% of the time. Unfortunately, this 3cm cutoff doesn’t track well with the current staging system, where T1a <4cm. Therefore, studies that use RFA on “T1a” tumors could have significant contamination with tumors >3cm. Lastly, RFA is good only for exophytic tumors because of the thermal sink caused by blood flow in the renal pelvis that reduces success rates for most endophytic tumors.

Cryoablation is also a very successful technique. Data demonstrate a 83-98% RFS, 81-100% DFS, and 94-100% CSS. In contrast to RFA, cryoablation can be used in larger T1b tumors and in endophytic/central tumors. Unlike RFA, cryoablation offers a much better 3yr RFS (75% vs. 98%, respectively). Since multiple needles can be placed to expand the treatment ice ball, cryoablation is useful in larger, and potentially more aggressive-appearing tumors. Indeed, Dr. Atwell presented images of a patient treated with cryoablation that had central invasion and possible segmental vein involvement.

He cautions that nephrometry scoring systems, while useful, may have limited applicability when evaluating ablative techniques. These scoring systems, such as RENAL and PADUA, were created in the surgical patient population. Multiple retrospective studies have been conducted, but it doesn’t appear that nephrometry tracks well with treatment effectiveness or recurrence risk.

A recent prospective study by Thompson et al. comparing ablation to the gold standard partial nephrectomy (PN) showed that ablation appears to compare more favorably than initially expected on historical data. Evidence shows no change in renal function compared to PN – especially since renal parenchymal preservation may be the most important determinant of postop renal function. Furthermore, ablation has an excellent pain profile and demonstrates good scores on overall physical and social well-being metrics.

It is important to note that the ASCO guidelines still state PN is standard of care for SRMs. But if complete ablation possible, then ablation should be considered. It is imperative for Interventional Radiologists and Urologists to have a good working relationship to collaborate with these patients and offer the best treatment options in an evidence-based but personalized approach.

With the technical aspects of these techniques continually improving, one would expect the survival and recurrence-free outcomes from ablation to continue to improve.

First Author: Ridwan Alam, BS, The Johns Hopkins University School of Medicine

Written By: Benjamin T. Ristau, MD, Society of Urologic Oncology Fellow, Fox Chase Cancer Center

at the 2017 Genitourinary Cancers Symposium - February 16 - 18, 2017 – Orlando, Florida USA

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