Optimizing prostate biopsy techniques.

W hat is the optimal biopsy strategy for detecting clinically important prostate carcinoma? I am not sure we are any closer in 2007 than we were in 1989 when the 6-core biopsy technique became the standard of care. Take too few cores and clinically significant cancers might be missed. However, take too many cores and clinically indolent cancer may be identified. Data from the early 1990s demonstrated that a significant number of cancers were being missed with a 6-core approach, particularly in larger glands. The solution has been to increase the number of cores which has improved the cancer detection rate to approximately 40%. The cost has been potential over detection. The 3 variables of tumor volume, tumor location and prostate gland size alter the likelihood of cancer detection. There is increasing evidence that we should take these 3 variables into account when tailoring our biopsy schemes to maximize the detection of clinically significant prostate cancer and minimize the identification of potentially indolent cancers. Transperineal saturation biopsies hold the promise of detecting anterior tumors that may have been missed with transrectal biopsy strategies. Furuno et al demonstrated that on repeat biopsy in high risk patients, the anterior region of the prostate harbors cancers which cannot be detected with standard biopsy techniques. Increasing the number of cores for larger prostates allows us to find prostate cancer foci that may be missed with standard techniques. Remzi et al developed a nomogram that incorporates prostate size and patient age to maximize the detection of prostate carcinoma in the prostate specific antigen (PSA) range of 2 to 10 ng/ml. In a prospective evaluation of the nomogram they demonstrated an improved cancer detection rate, particularly in younger patients. Unfortunately both of these strategies potentially increase the likelihood of detecting indolent disease. In this issue of The Journal Serfling et al (page 2352) address this important concept by constructing a mathematical model that examines the effect of prostate volume, number of cores, biopsy core location and tumor volume on cancer detection. The tumor volumes examined were 1.0 and 3.0 cc, well above the conventional thresholds of 0.2 and 0.5 cc for a pathologically indolent tumor. Prostate volumes of 20 to 80 cc were placed in the model, resulting in core number recommendations ranging from 4 to 22. The novel concept is that a smaller prostate with a larger tumor needs fewer cores to maintain a detection probability of 0.90. Implicit in this approach is that some smaller, presumably less significant tumors will be missed. Conceptually this model is attractive. If it is accurate, urologists could limit the number of cores in a small gland, maintaining the ability to detect larger tumors but decreasing the likelihood of detecting insignificant tumors. Before