Significance of prostatic biopsies after radiation therapy for carcinoma of the prostate
The significance of a prostatic biopsy after radiation therapy for prostatic cancer is at present uncertain. Criteria for interpreting residual tumor cells as viable and, more important, determining whether such cells are biologically capable of local growth and/or subsequent dissemination, by histological evaluation, require further clinical correlation and studies designed to better characterize biological behavior and growth potential of neoplastic cells in general and how this may or may not be altered by irradiation. A positive biopsy after radiation therapy must be regarded, however, as ominous simply because its potential significance is yet to be determined. Prostatic biopsies may predict treatment failure in general, but their significance relative to an individual patient requires correlation with 1) tumor stage, grade, size, and site of the original tumor; 2) technique of biopsy, number of cores obtained, and the location relative to the original tumor; 3) time interval of biopsy after treatment and whether biopsy is performed on one or more occasions; 4) circumstances (clinical progression or clinical regression) at the time of biopsy; and 5) treatment artifacts regarding dose delivered and distribution, which is especially important with regard to interstitial irradiation.