Increasing the number of biopsy cores before renal cryoablation increases the diagnostic yield

Renal cryoablation has been established as a primary management option for many small renal masses. Biopsy is performed intraoperatively and typically consists of one core being taken. This method was used to reduce the potential for seeding tumor and to minimize bleeding, although there have been no reports of tumor formation caused by biopsy seeding and blood loss is minimal. It is also associated with a relatively high yield of nondiagnostic cores. As such, in March 2005, we began taking three biopsy cores rather than one in an attempt to decrease our nondiagnostic rate.

Biopsy results were retrospectively reviewed for patients who underwent renal cryoablation by two surgeons between February 2001 and July 2007. Findings were stratified according to the number of cores taken, which was either one or three. Tests for significance were performed using the chi-square test to determine if there was a difference in the nondiagnostic rates and the cancer yield rates.

Results of 119 biopsies were reviewed. Of those, a single core was taken from 81 (68%) lesions. Of these, 49 (60%) were malignant and 14 (17%) were nondiagnostic. The remaining 38 (32%) had three cores taken. Twenty-seven (71%) of these were malignant and two (5%) was nondiagnostic. The P values for cancer yield rates and nondiagnostic rates were 0.248 and 0.030, respectively.

Using a three-core biopsy strategy resulted in an 11% increase in cancer yield and a 12% reduction in nondiagnostic rate. Decreasing the nondiagnostic rate may help in counseling patients at follow-up. Continued investigation is warranted and under way.