Radiofrequency ablation (RFA) of small renal tumors is safe and effective, and is associated with high rates of disease-free survival, according to a study that followed patients for up to 10 years.
In 106 patients who had a total of 112 tumors and who were followed for a median 79 months, 10 recurrences were seen, after an initial procedural success rate of 97%.
Over a 6-year period, Kaplan-Meier disease-free survival (DFS) was 89%, and cancer-specific survival (CSS) was 96%. In the subgroup followed for 10 years, DFS was 82%, CSS was 94%, and overall survival (OS) was 49%.
Tumors were, on average, small (mean 2.5 cm), but for patients whose tumors were larger than 3 cm, the DFS rate fell to 68%. Patients were included in the study if they had a solitary renal mass; those who had metastatic renal cell carcinoma (RCC) or a hereditary kidney cancer syndrome were excluded.
Brett Johnson, MD, and his collaborators from the University of Texas Southwestern, Dallas, noted that an additional 29 patients received RFA but also had partial nephrectomy; these patients were excluded. “Healthier patients with larger tumors may have been advised to undergo partial nephrectomy, thereby selecting for more comorbid patients for RFA,” they noted in discussing their findings. The report was published in
Within these parameters, Dr. Johnson and his colleagues conducted a retrospective review of clinic patients whose renal tumors were successfully treated with RFA between the years 2000 and 2007. Patients were followed with yearly imaging, and were considered to have a recurrence if contrast enhancement was seen within the ablation zone at any point after a negative imaging study.
Of the 10 recurrences that were seen, eight were local and two were local and metastatic. An additional patient developed metastatic RCC without evidence of local recurrence; all patients with metastases died of their disease, said Dr. Johnson and his coauthors.
For patients whose tumors recurred, the mean initial tumor size was 3.2 cm, compared with 2.4 cm in those whose tumors didn’t recur (P = .005). Looking at the tumor size data another way, tumor size “was an independent risk factor for cancer recurrence,” with an odds ratio of 3.01 (P = .025), wrote Dr. Johnson and his collaborators.
They noted that it was not routine practice for biopsies to be performed during the initial study period; the seven patients with recurrences who had biopsy data all had clear cell RCC. Median time to local recurrence was 26 months, with no recurrences seen after 5 years.
At the time of the initial procedure, patients were a mean 63.1 years old. The relatively low OS in the subgroup with 10 years of follow-up was likely related to advancing age.
In the subgroup analysis of patients for whom 10-year data were available, the investigators used only data from patients whose initial tumors were biopsied when calculating CSS and metastasis-free survival; these rates were both 94% for those analyzed.
“Age, gender, and time of follow-up had no statistically significant effect on disease-free recurrence” in a univariate analysis, said Dr. Johnson and his colleagues.
“Nephron sparing surgery is the gold standard for treatment of small renal masses,” and the study bolsters the safety and durable efficacy of RFA by using actual survival data rather than actuarial disease survival, said the investigators.
The current study is unique in having such a long duration of follow-up and a subgroup of individuals with 10 years of annual imaging data. In addition, experienced urologists at a single site all used a uniform technique to perform thermal ablation on solitary tumors, noted Dr. Johnson and his coauthors. Successful ablations were followed only by surveillance, in keeping with current American Urological Association recommendations.
However, the study’s retrospective, nonrandomized nature introduces the possibility of selection bias, and variations in follow-up protocols may be a source of ascertainment bias, they said.
The authors reported no conflicts of interest and no outside sources of funding.
SOURCE: Johnson B et al. J Urol. 2018.