Our research has led us to believe that percutaneous image-guided ablation of small renal tumours may be considered safer than surgical nephrectomy and equally effective in attaining long-term cancer-free survival, writes Konstantinos Katsanos.
With increasing numbers of renal cell carcinomas being diagnosed annually, we are continuously looking for ways to evaluate and find the optimal treatments for small renal tumours. Current clinical practice guidelines from the European Association of Urologists (EAU) and the European Society of Medical Oncology (ESMO) recommend partial nephrectomy as the gold standard nephron sparing treatment for all small renal tumours (<7cm) and that radiological image-guided ablation (thermal or cryoablation) should be reserved for a patient population deemed unfit for surgery; such as elderly patients, those with significant comorbidities, high surgical risk, solitary kidney, already compromised renal function, hereditary renal cell carcinoma and/or multiple bilateral tumours.
However, there is actually very limited comparative evidence between radiological ablation and surgical partial nephrectomy for early stage renal cell carcinoma to support those guidelines. Recently published observational studies have shown that both partial nephrectomy and thermal or cryoablation of small renal tumours offer excellent oncological outcomes for the treatment of stage T1a renal cell carcinoma (up to 4cm) with acceptably low perioperative morbidity and similar long-term oncologic outcomes. Ablation has consistently demonstrated fewer perioperative complications with a somewhat higher need for repeat treatment, whereas partial nephrectomy has shown a slightly lower rate of local recurrence and/or remote metastases. Long-term data following open or laparoscopic partial nephrectomy of 894 small T1a renal cell carcinomas from a single centre retrospective study have shown a five-year recurrence-free survival of 97.8% and 97.1% for laparoscopic and open partial nephrectomy, respectively. Another single-centre retrospective series of radiofrequency ablation in 185 patients with small renal tumours reported a five-year recurrence-free survival of 96.1% for T1a lesions (<4cm). Hence, long-term disease-free survival following percutaneous ablation appears to be non-inferior compared to nephron-sparing partial nephrectomy and both treatments are usually curative with reported survival outcomes well exceeding 95% at five years.
This suggests that there is a pressing need for high-quality comparative effectiveness research between the historical standard of surgical partial nephrectomy and the less-invasive and potentially cheaper image-guided percutaneous ablation. In 2014, we performed a systematic review and meta-analysis (quantitative evidence synthesis) of six cross-sectional studies (including one randomised study) including 587 patients with small renal tumours (average tumour size 2.5cm). Using a random effects model, we combined 335 patients treated with open or laparoscopic nephrectomy (mostly partial) and compared them with 252 cases treated with thermal ablation (mostly percutaneous) with available follow-up up to five years.
Interestingly, we found that overall complication rate was significantly lower in the ablation group (7.4% vs. 11%; risk ratio: 0.55, 95% confidence interval [CI]: 0.31-0.97, p=0.04) and postoperative renal function was significantly worse in case of nephrectomy (mean difference of estimate glomerular filtration rate (eGFR) decline: -14.6ml/min/1.73m2, 95% CI: -27.96 to -1.23, p=0.03). Future local recurrence rate was identical in both groups (3.6% vs. 3.6%; risk ratio: 0.92, 95% CI: 0.4-2.14, p=0.79) and disease-free survival was also similar (hazard ratio: 1.04, 95% CI: 0.48-2.24, p=0.92).
We have just repeated our literature search and the aforementioned meta-analysis in order to include some more recent studies. An updated synthesis of nine studies including 2,480 patients in total (841 with thermal ablation vs.1,639 with partial nephrectomy) has shown again nearly identical comparative freedom from recurrent renal cancer or metastasis (hazard ratio: 1.05, 95% CI: 0.70-1.58, p=0.81). Consequently, we believe that percutaneous image-guided ablation of small renal tumours may be considered safer than surgical nephrectomy and equally effective in attaining long-term cancer-free survival. We therefore believe that percutaneous ablation should be offered alongside partial nephrectomy in younger low surgical risk patients with stage T1a renal cell carcinoma.
Konstantinos Katsanos is a consultant vascular and interventional radiologist, St. Thomas’ Hospital, London, UK. His twitter handle is @DrKKatsanos