Clinical and pathologic tumor characteristics of prostate cancer as a function of the number of biopsy cores: a retrospective study.

OBJECTIVES

Many men with negative prostate biopsies and persistently elevated serum total prostate-specific antigen (tPSA) values will have cancer detected on a repeated biopsy. An important issue is whether the cancer would have been detected on the initial biopsy had more biopsy samples been obtained. The objective of our study was to retrospectively characterize the clinical and pathologic tumor features associated with men who underwent sextant core biopsies compared with men who needed more than six core biopsies during one or more biopsy sessions to detect prostate cancer. Transrectal ultrasound (TRUS)-estimated prostatic volume was evaluated to determine whether the number of biopsy cores needed for prostate cancer detection was influenced by gland size.

METHODS

We retrospectively evaluated the number of biopsy core samples obtained in 185 men (mean age 63+/-6 years) enrolled in our PSA-based screening study for prostate cancer who were found to have prostate cancer and elected radical prostatectomy as treatment. Correlation coefficients were calculated and univariate analyses were performed to evaluate clinical (age, tPSA, TRUS volume, PSA density) and pathologic (Gleason score, pathologic weight, organ confinement, "possibly harmless" cancer) characteristics associated with men who required more biopsy cores to detect the cancer.

RESULTS

Of the 185 men, 103 (56%) had 6 or fewer total biopsy cores taken and 82 (44%) had more than 6 cores (44 [24%] of 185 had 7 to 12 cores and 38 [20%] of 185 had 13 or more cores). There was a positive correlation between age, serum tPSA, TRUS-determined prostate volume, and pathologic specimen weight and an increasing number of total cores (all P values < 0.05). The number of biopsy cores was not associated with PSA density, Gleason score, cancer volume, organ confinement, or "possibly harmless" cancers (all P values > 0.05). Men with a TRUS volume 30 cc or less (46%) required a mean of 8 total cores to detect the cancer compared with a mean of 11 cores (P = 0.003) in men with a TRUS volume greater than 30 cc (54%). A greater percentage of men with a TRUS prostate volume greater than 30 cc compared with men whose volume was 30 cc or less would have had their cancer missed with only a six-core biopsy (64% versus 46%, P = 0.01).

CONCLUSIONS

Sextant core biopsies may be inadequate to detect prostate cancer in some men. These data support the performance of more than six core biopsies to detect clinical prostate cancer. A prospective trial using TRUS-determined prostate volume to determine the number of cores to take is needed to accurately assess this issue.