Among patients with renal cell carcinoma (RCC), a type of kidney cancer, those with larger tumors may yield the most benefit from stereotactic body radiotherapy (SBRT) with the least rate of severe complications compared with other ablative options, according to research published in The Lancet.
In a review of 133 studies, of which included 8,910 patients with RCC, local control rates for SBRT were 99% at one year, 97% at two years and 95% at five years. Comparatively, these numbers were 96%, 95% and 92% for radiofrequency ablation; 97%, 95% and 86% for microwave ablation; and 95%, 94% and 90% with cryoablation. Overall, these findings suggest that SBRT may be a better option for treating larger tumors; however, for smaller, peripheral tumors, all the approaches continued to be effective choices.
“All investigated ablative methods continue to represent effective treatment choices in RCC, and these findings support multi-disciplinary discussions of these treatment methods, along with surgery and surveillance, to individualize treatment decisions in these patients,” first study author Dr. Ryan S. Huang wrote in the journal. “Future research should aim to conduct randomized controlled trials across larger patient populations to further elucidate the long-term oncological and survival outcomes associated with these treatments.”
Glossary:
Meta-analysis: a statistical technique that combines the results of multiple independent studies to produce a single, comprehensive analysis.
Stereotactic body radiotherapy (SBRT): a cancer treatment that delivers highly concentrated doses of targeted radiation to a single or solitary tumor.
Ablative: treatment that uses heat or cold to destroy, or ablate, cancer tumors without the need for more invasive surgery.
Radiofrequency ablation: a minimally invasive medical procedure that uses radiofrequency energy to destroy abnormal tissue.
Microwave ablation: a minimally invasive cancer treatment that uses microwave energy to generate heat and destroy tumor cells.
Cryoablation: a medical procedure that uses extreme cold to destroy abnormal or diseased tissue.
Huang currently works as a part of the Temerty Faculty of Medicine at the University of Toronto, in Ontario, Canada.
RCC is the most common type of kidney malignancy, making up over 90% of kidney cancer cases. Over the past 20 years, the number of cases has steadily increased by approximately 2% each year. While surgery — either partial or complete kidney removal — has long been the standard treatment, it may not be suitable for all patients, particularly older individuals or those with existing health conditions that make surgery risky. As a result, new approaches have emerged that can effectively treat the cancer while preserving kidney function. Among these options, stereotactic body radiotherapy (SBRT), radiofrequency ablation, microwave ablation and cryoablation have gained attention as effective alternatives.
Radiofrequency ablation and microwave ablation destroy cancer cells using heat, while cryoablation freezes them. These techniques are already included in major medical guidelines, particularly for small tumors less than 3 to 4 centimeters in size, due to their effectiveness and minimally invasive nature. SBRT, a newer method, uses precise, high-dose radiation over a few sessions and has shown promising results with fewer side effects. However, unlike the other methods, SBRT has not yet been tested in large, randomized trials comparing it directly to these established treatments.
To address this gap, investigators shared that their research systematically reviewed and compared the effectiveness and potential side effects of these treatments in order to help guide doctors and patients in making informed decisions about managing kidney cancer.
Delving Into the Methods of Research
To conduct this meta-analysis, investigators utilized medical research databases to find studies published between January 2000 and March 2024 that examined the effectiveness of SBRT, radiofrequency ablation, microwave ablation and cryoablation in localized kidney cancer. The review included peer-reviewed studies that reported treatment outcomes in adult patients and had at least five participants, excluding studies focusing on metastatic kidney cancer, benign kidney tumors, re-treatment cases or studies that combined multiple treatment methods in a way that made it impossible to measure individual effects. Studies that lacked complete data, were not available in English or were unpublished were also excluded.
Two independent reviewers worked together on a sample set of studies to ensure they were applying the same selection criteria consistently and examined the full texts of the eligible studies thereafter. Notably, the primary outcomes were one-year, two-year and five-year local control, which investigators defined as the proportion of patients with no evidence of tumor progression, growth or recurrence. One-year, two-year and five-year cancer-specific survival rates; one-year, two-year, and five-year estimated glomerular filtration rates and side effects served as the studies secondary outcome measures.
Regarding safety, the number of patients who reported grade 3 (severe) or grade 4 (life threatening or disabling) after cryoablation, radiofrequency ablation, microwave ablation and SBRT was 3%, 2%, 1% and 2%. Notably, the authors said that the risk of bias in most studies was moderate, though no publication bias was observed.
“[Their] findings suggest that all methods are highly effective and safe for small tumors [less than 4 centimeters]; however, for larger tumors [equal to or more than 4 centimeters], SBRT might offer improved local control. These results expand on previous meta-analyses comparing only radiofrequency ablation, microwave ablation and cryoablation, which have shown comparable pooled clinical efficacy and five-year overall survival in patients with small renal tumors [less than 4 centimeters],” Huang and authors wrote
“Future research should aim to conduct randomized controlled trials across larger patient populations to further elucidate the long-term oncological and survival outcomes associated with these treatments. We encourage a multi-disciplinary approach to the selection and design of ablative therapies to treat primary renal cell carcinoma, and individualized decision making is necessary to optimize patient treatment outcomes,” they concluded.
Reference: “Comparative efficacy and safety of ablative therapies in the management of primary localized renal cell carcinoma: a systematic review and meta-analysis” by Dr. Ryan S. Huang, et al., The Lancet.
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