Commentary on "Cytoreductive radiofrequency ablation in patients with metastatic renal cell carcinoma (RCC) with small primary tumours treated with sunitinib or interferon-α."

Objectives: To evaluate the role of cytoreductive radiofrequency ablation (cRFA) in patients with metastatic renal cell carcinoma (RCC) with small primary tumours treated with immuno- or targeted therapy. To assess the efficacy of sunitinib in patients with metastatic RCC with unresected small primary tumours. Patients and methods: Three parallel single-arm prospective studies were conducted. Eligibility criteria were nearly identical for all trials and included: histopathologically confirmed RCC; metastatic measurable disease; size of primary tumour <5. cm; good or intermediate prognosis according to the Memorial Sloan-Kettering Cancer Center model; and no previous therapy. Study 1: Patients were treated with percutaneous cRFA under computed tomography guidance followed by interferon (IFN)-α, 9 MIU, s.c., three times per week. Study 2: Patients received cRFA followed by sunitinib in repeated 6-week cycles of 50. mg/day orally for 4 weeks, then 2 weeks off treatment. Study 3: Patients with unresected primary RCC received sunitinib alone. The primary endpoint was progression-free survival (PFS). Results: Baseline patient characteristics (age, gender, histology, Eastern Cooperative Oncology Group performance status, metastatic sites, primary tumour size) were similar in all three studies. Efficacy data for 114 evaluable patients showed an objective response rate of 8% (95% confidence interval [CI] 4.5, 10.5) for study 1, 28.9% (95% CI 15.2, 34) for study 2, and 31.6% (95% CI 20.3, 38.9) for study 3. The median (95% CI) PFS times were 9.1 (6.9, 10.2), 13.4 (9.8, 14.4) and 12.7 (11.3, 13.5) months for studies 1, 2 and 3, respectively. Objective response rate was significantly higher and PFS significantly longer in the sunitinib trials than in study 1 (P<0.01 all differences); no differences were found between studies 2 and 3 (objective response rate, P = 0.1; PFS, P = 0.6). Study 1 met its primary endpoint, showing that PFS was significantly longer than the expected 5 months (P = 0.02). The median (95% CI) objective survival (OS) times were greater in study 2 (cRFA/sunitinib) and study 3 (sunitinib-alone) than in study 1 (IFN-α) at 27.2 (22.6, 31.8) and 22.5 (20.7, 24.3) vs 19.5 (16.3, 22.7) months, respectively. Differences were significant (study 1 vs 2, hazard ratio [HR] = 0.55; P = 0.003; study 1 vs study 3 HR = 0.6, P = 0.01). OS was significantly longer in the cRFA/sunitinib group compared with the sunitinib-alone group (HR = 0.71; P = 0.04). There were no unexpected toxicities of medical treatment or complications of cRFA. Conclusions: cRFA is a safe and effective approach for select patients with metastatic RCC treated with immunotherapy. The cRFA technique did not improve PFS in patients treated with sunitinib; cRFA probably has impact on OS in these patients. This needs to be tested in a larger trial. Sunitinib was effective in patients with metastatic RCC with unresected small primary tumours.