Using the Surveillance, Epidemiology and End Results (SEER)-Medicare database, Alessandro Larcher, MD, of the University of Montreal Health Center in Montreal, Canada, and colleagues studied 1,860 patients with cT1a kidney cancer managed with either local tumor ablation (LTA) or observation (OBS) from 2000 to 2009. Of these, 553 (30%) underwent LTA and 1,307 underwent OBS.
After propensity-score matching, 553 LTA and 553 OBS patients remained for analyses. The 5-year cancer-specific mortality (CSM) estimates were 3.5% for the LTA group compared with 9.1% of the OBS group. According to the investigators, these estimates result in a 5.6% absolute CSM difference. This difference indicates that the use of OBS instead of LTA in 18 patients may contribute to 1 potentially avoidable cancer-specific death, Dr. Larcher’s team reported online ahead of print in BJU International. In multivariable analysis, LTA was associated with a significant 53% decreased risk of CSM compared with OBS.
“These important observations are relevant with respect to clinical decision-making, when LTA is weighed against OBS, especially in the elderly,” the authors wrote.
Compared with patients in the OBS group, those in the LTA group were significantly younger (median age 77 vs. 78 years), more likely to be white (84% vs. 78%), more frequently married (59% vs. 52%), and more frequently of high socioeconomic status (54% vs. 45%).
The researchers acknowledged that the study was limited by its retrospective design. Another limitation was their definition of OBS, which was the absence of any primary treatment, regardless of patients’ specific follow-up protocol. “In this context, it cannot be directly compared with meticulous active surveillance protocols,” the authors pointed out.
The important difference in terms of CSM-free survival observed between the LTA and OBS groups, the investigators stated, might not be applicable to candidates for active surveillance protocols, where timely treatment is administered in cases of early progression. This would eventually attenuate the difference between the LTA and OBS groups with respect to CSM-specific survival, they said.
Commenting on the new study, Hiten D. Patel, MD, MPH, a urological surgery resident at the James Buchanan Brady Urological Institute at Johns Hopkins Medical Institutions in Baltimore, noted that previous SEER studies already have established that surgical management is superior to observation (or “nonsurgical management”). The more relevant group to compare with LTA is an active surveillance cohort, he said. With an observation cohort, the question remains as to why patients did not receive active treatment, he said.
“Inherently, no amount of adjustment or matching can overcome residual confounding in the comparisons,” said Dr. Patel, who has conducted outcomes research comparing surgical and nonsurgical management in patients with localized kidney cancer. “The observation group is more an estimation of population-based practice rather than surveillance, and shows there are individuals who do not obtain intervention, whether ablation or surgery, for a variety of reasons and could possibly benefit from some type of therapy.”