NEW ORLEANS, LA USA (UroToday.com) - Although 30% of small renal masses are benign, many are still being treated by excision or ablative approaches without a pretreatment biopsy. It has been demonstrated in various centers that a percutaneous renal tumor biopsy (RTB) is a safe and effective procedure to preoperatively identify the histology of renal cell tumors, including oncocytomas. The authors’ concern, however, is in the difficulty of differentiating between oncocytomas and their malignant counterpart, chromophobe renal carcinoma (chRCC), based solely on just RTB. Therefore, their primary objectives were to present their experience with conservative management of oncocytomas, to compare oncocytomas’ growth rate with that of chRCCs managed by active surveillance, and to assess clinical and pathological factors associated with the growth rate.
The authors carried out a single center, retrospective study that included 110 patients diagnosed with oncocytoma following RTP or surgery between 2003 and 2014. Patients who had masses with less than 12 months of imaging follow up were excluded, thus leaving a total of 80 patients for analysis. Using a mixed effect linear model, a random intercept, and random slope, the average growth rate was estimated. Patient demographics and lesion characteristics were also collected for growth rate analysis.
Overall, 95 lesions were included in the study analysis, 81 of which were oncocytomas and the remaining 14 were chRCCs. Over the course of 3 years, growth was observed in 75% of oncocytomas and 64% of chRCC lesions. Adjusting for the initial tumor size, the average growth rate was determined to be 0.14 cm/year and 0.38 cm/year for oncocytomas and chRCCs, respectively. The difference in these growth rates was statistically insignificant (p = 0.534).
The authors concluded that a majority of oncocytomas will naturally grow over time with an average growth rate of 0.14cm annually. Diagnosis based on RTB histology, however, can be examined with regular routine imaging. Furthermore, patients on surveillance should be made aware that a growth is not necessarily a sign of malignancy.
Presented by Patrick O. Richard at the American Urological Association (AUA) Annual Meeting - May 15 - 19, 2015 - New Orleans, LA USA
University of Toronto, Toronto, ON Canada
Reported by Rebecca Do (University of California-Irvine), medical writer for UroToday.com