Seminal vesicle biopsy: accuracy and implications for staging of prostate cancer

Seminal vesicle biopsy (SVB) is a new technique for detecting the spread of prostate cancer to the seminal vesicles. A comparison of findings following SVB in patients undergoing radiation therapy with pathologic findings following radical retropubic prostatectomy (RRP) was made to evaluate the accuracy of this test and its use in the staging of prostate cancer.

Four hundred nine patients with clinically localized adenocarcinoma of the prostate gland were evaluated for treatment: 222 patients underwent SVB prior to radiation therapy and 187 patients underwent RRP. Clinical stages in patients undergoing SVB included T1a (1 patient), T1b (4), T1c (35), T2a (49), T2b (96), and T2c (37); RRP clinical stages included T1b (3 patients), T1c (48), T2a (57), T2b (66), and T2c (13). The Gleason scores in patients undergoing SVB were 2 to 4 in 50 men, 5 to 6 in 110 men, and 7 and greater in 62 men; the Gleason scores in patients undergoing RRP were 2 to 4 in 53 men, 5 to 6 in 94 men, and 7 and greater in 40 men. Prostate-specific antigen (PSA) values ranged from 1.3 to 190 ng/mL (median 10.75) in men undergoing SVB and ranged from 0.5 to 140.6 ng/mL (median 9.0) in men undergoing RRP.

The overall incidence of seminal vesicle involvement as determined by the two techniques was the same. Seminal vesicle involvement was found in 33 of 222 patients (15%) undergoing SVB and in 27 of 187 (14%), of the RRP specimens (P = 0.9). When the two groups were further divided by three prognostic categories (clinical stage, PSA level, and grade), there was no difference in the incidence of seminal vesicle involvement between the two methods, except in the patients with Gleason score of 4 or less. In these patients, 5 of 53 (9%) had seminal vesicle involvement in the RRP group, compared with none of the 50 men in the SVB group (P = 0.02). Disease that was not organ confined was found in 69 of 187 prostatectomy specimens (37%). Of these patients, 27 of 69 (39%) had seminal vesicle involvement.

SVB is an accurate method of detecting seminal vesicle invasion based on comparisons with radical prostatectomy findings. Its importance lies in its ability to detect a large percentage of patients with non-organ-confined disease and in its use in modifying treatment planning accordingly.