ASCO GU 2017: Use of Ablation in Small Renal Tumors

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 D. Atwell of the 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 radiofrequency ablation (RFA) or microwave ablation and cold ablation (cryoablation). Dr. Atwell warned 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 an 88%-to-98% recurrence-free survival (RFS), a 75%-to-95% disease-free survival, and an 80%-to-100% cancer-specific survival. RFA is good for small tumors, with 97%-to-100% successful treatments for tumors smaller than or equal to 3 cm, whereas treatment for tumors larger than3 cm is only successful 60% to 86% of the time. Unfortunately, this 3-cm cutoff does not track well with the current staging system, where T1a is smaller than 4 cm. Therefore, studies that use RFA on “T1a” tumors could have significant contamination with tumors bigger than 3 cm. Lastly, RFA is good only for exophytic tumors because of the thermal sink caused by blood flow in the renal pelvis, which reduces success rates for most endophytic tumors.

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

He cautioned 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 is not apparent that nephrometry tracks well with treatment effectiveness or recurrence risk.

A recent prospective study by Thompson and colleagues comparing ablation with the gold-standard partial nephrectomy (PN) indicated that ablation seems to compare more favorably than initially expected on historic data. Evidence showed no change in renal function compared with 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 American Society of Clinical Oncology guidelines still state that PN is standard of care for SRMs. But if complete ablation is possible, then ablation should be considered. Interventional radiologists and urologists must have a positive 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, Dr. Atwell concluded, survival and recurrence-free outcomes from ablation are expected to continue to improve.

Presenter: Alessandro Volpe, MD university of south piedmont, Italy

Written By: Shreyas Joshi, MD, Fox Chase Cancer Center

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

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