Characterization of prostate cancer missed by sextant biopsy.

There is a trend to increase the number of prostate biopsies taken to increase the detection rate of prostate cancer. We examined radical prostatectomy specimens and correlated the findings to those of preoperative sextant biopsy in an effort to identify the characteristics of tumors that went undetected by our biopsy regimen. Seventy-one patients diagnosed with prostate cancer based on sextant biopsy who underwent radical prostatectomy at our institution from June 1995 to November 2001 had prostatectomy specimens and biopsy slides reviewed. These specimens were step-sectioned and whole-mounted. The location, size, and grade of individual cancer foci in the prostatectomy specimens were correlated with results of the original sextant biopsies. Clinically significant tumors were defined as those with volume > 0.5 mL or Gleason score > or= 7 and extracapsular extension. In 33 patients (46%), there was concordance of biopsy and prostatectomy findings. In 38 patients (54%), additional lesions were demonstrated in the prostatectomy specimens that were not detected by our sextant biopsies. These included 13 cases (34%) with tumors > 0.5 mL and 25 cases in which the lesions were < 0.5 mL in size. However, 7 of these cases contained tumors with Gleason score > or =7. Tumors were located in the transition zone in 8 of these 38 cases (21%), and the remaining tumors were located in the peripheral zone (79%). No tumors with extracapsular extension were missed. Thus, 20 of the 71 cases (28%) had clinically significant cancers that went undetected by the traditional sextant biopsy method. Greater than 50% of patients who underwent sextant biopsy of the prostate had additional tumors that were missed when compared to the pathologic specimen. As many as 28% of these patients had clinically significant cancer based on size and grade criteria. A strategy of increased numbers of biopsies would improve the detection rate of these clinically important tumors. However, the ideal strategy for optimizing cancer detection requires further investigation because increased numbers of biopsies would also increase detection of clinically insignificant tumors.