Irrespective of the forthcoming 5-year data, percutaneous cryoablation has already carved a permanent place on the list of RCCa treatment options, writes Christos Georgiades, Assistant Professor of Radiology and Surgery, Johns Hopkins Hospital.
Every so often in medicine, a combination of seemingly unrelated events precipitates (or threatens, depending on your point of view) a change in the status quo. Albeit in the early stages, we are now witnessing such a transition in the treatment of renal cell carcinoma (RCCa). There are many factors contributing to this transition. In the United States there has been a steady and significant increase in the use of cross-sectional imaging studies as part of the patient’s primary diagnostic work up; so much so, that some in jest note that the physical exam has been outsourced to Radiology. To a lesser extent, the same trend is evident in Europe.
Mainly due to incidental detection (but also due to the increase in obesity rates, a known risk factor for RCCa), the incidence of RCCa has been steadily increasing on both sides of the Atlantic and in 2008 stood at 55,000 in the USA and 35,000 in Europe. Since there has been an increase in incidental detection, there has also been earlier detection of RCCa. This is why lesion size at diagnosis has decreased; 70% of detected lesions are smaller than 4cm. Another related factor is the evolution of cryoablation technology and the development of thin and more effective cryoprobes that allow for a percutaneous approach. The nature of RCCa itself is also important. It is always mass forming and not infiltrating and very slow growing (RCCa doubling time 603.1 +/- 510.1 days). The retroperitoneal location of the kidney mitigates bleeding complications and the fact that it is surrounded by fat allows for generous ablation margins.
All these factors have set the stage for the next step, which was to test cryoblation in clinical practice. During the last few years, a number of studies have been published showcasing the safety and efficacy of percutaneous cryoablation for RCCa. Although none of these was a prospective, randomized study, remarkably, they all arrived at the same conclusions: that for lesions <4cm, the efficacy of the procedure is approximately 95% and the rate of significant complications 6-8%.
These numbers compare very favourably with laparoscopic cryoablation and even nephron sparing surgical options. There is however, one catch – long term data are lacking. Precisely because of the slow growing nature of RCCa, 1- or 2-year data may not be adequate. Justifiably, referring physicians expect 5-year data before drawing any conclusions. Based on the time of publication of most of the 1- and 2-year data, the first 5-year efficacy results are expected to be released during the next 1-3 years.
Even so, the number of patients undergoing percutaneous cryoablation for RCCa will continue to increase. Given the preliminary but nevertheless very encouraging results, the group of patients that can benefit immediately are those who are, for whatever reason, unable to undergo surgery or general anaesthesia. Most such patients were previously simply being followed up, a not unreasonable option for older individuals given the expected RCCa growth rate. Others who might benefit could be a small percentage of patients, those with RCCa predisposing syndromes, multiple tumours or previous nephrectomy, who are likely to be steered towards ablation. There is yet another group of patients who will contribute to the increase in the use of percutaneous cryoablation. These are patients who simply do not want to have surgery, when given a reasonable alternative. Most members of this group usually independently research treatment options and stumble across ablation. The internet has been a catalyst for this group of patients, whose decision to forgo surgery and pursue ablation is further fuelled by the fact that a possible failure of cryoablation does not preclude surgery.
Irrespective of the forthcoming 5-year data, percutaneous cryoablation has already carved a permanent place on the list of RCCa treatment options. If the 5-year efficacy data confirm the earlier results, (going by unpublished data, this is likely) then percutaneous cryoablation may become the most important nephron-sparing treatment option for patients with small and percutaneously approachable RCCa. Not bad for an option many times less expensive than the current gold standard, one requiring only minimal sedation and one that can be performed mostly on an outpatient basis!