Risk factors for perineal seeding of prostate cancer after needle biopsy.

Between 1975 and 1986, 2,107 perineal prostate biopsies were performed at our institution with 502 (23.8 per cent) positive for prostate cancer. Among this group there were 5 cases (1.0 per cent) of perineal seeding. These 5 cases along with a case referred to our institution represent cases 14 to 19 in the literature. All 19 cases are reviewed to elucidate risk factors for the development of perineal seeding. Biopsy of large volume local tumors appears to be the greatest risk factor associated with 18 of the 19 cases. Technique of biopsy appears to be important in that removal of the Tru-Cut sheath and obturator may expose the perineum to a greater risk of seeding. Other factors discussed include histology, hormonal responsiveness and radiotherapy technique. Distant metastases were discovered simultaneously or within 16 months of the perineal seeding in every case, and all patients died at a median of 36 months after initial diagnosis. Perineal seeding after prostatic needle biopsy is uncommon but its occurrence suggests a poor prognosis.