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Although needle biopsies are being used for localization, the majority of prostate cancers are multifocal in nature and invisible on gray scale ultrasonography.
This article discusses current biopsy techniques, their shortcomings, and the implications of their limitations for focal therapy.
In breast cancer, lumpectomies are often performed with the use of needle localization prior to surgery, allowing the surgeon some confidence in the excision of what is otherwise grossly normal-looking tissue. Likewise, focal therapy of the prostate will require either preoperative localization or use of a highly reproducible mapping of the tumor in 3-dimensional space, a goal that has yet to be achieved. Alternatively, one can treat areas of the prostate that are positive and repeat focal therapy for any subsequently positive foci. This may be reasonable, given the slow natural history of most prostate cancers. Arguably, these same tumors may have such low malignant potential that active surveillance may be a reasonable approach, as well.
Current biopsy techniques
Contemporary prostate biopsy techniques are limited in their ability to reliably predict location of the tumor within the prostate for several reasons. First, cancer detection is a function of the number of needle cores taken and the direction of the needle cores that are more lateral and toward the prostatic base. Studies have found that the classic sextant biopsy template results in a lower yield compared with contemporary methods that use more laterally directed cores and 10 to 12 samples (Urology 2001; 57:1112-6; J Urol 2006; 175:1605-12). Failure to adequately sample the prostate will therefore result in greater numbers of false-negative biopsies.