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Background. Although the incidence of positive postradiotherapy biopsies has been reported, the range is considerable (19-93%) and depends partly on patient-selection criteria. In addition, the prognostic significance of transrectal ultrasonography (TRUS) and prostate specific antigen (PSA) used alone and in combination in predicting residual cancer after radiotherapy has yet to be determined. Methods. Transrectal ultrasonography-guided prostate biopsies were performed on 31 unselected patients with prostate cancer 34-77 months (mean, 51 months) after definitive external beam radiotherapy was completed. Biopsy results were compared for pre- and posttreatment parameters (clinical stage, grade, PSA, and TRUS). Results. In 22 patients (71%), residual cancer was detected histologically by biopsy. All but one patient (12/13, 92%) with a pretherapy PSA value greater than 10 ng/mL had a positive biopsy compared with 50% of those (7/14) with a pretherapy PSA value less than or equal to 10 (P < 0.05). After radiotherapy, a positive biopsy was noted for 15 of 16 patients (94%) with a PSA value greater than 2 and in 20 of 23 (87%) of those with abnormal TRUS findings (P < 0.01 and P < 0.005, respectively). Conclusions. The most clinically useful model for predicting histologically identifiable residual cancer was either a serum PSA value greater than 2 or a PSA value less than or equal to 2 and abnormal TRUS findings. The positive and negative predictive values of the model were 84% and 83%, respectively. The model predicted biopsy results correctly in 26 of 31 patients (84%). Transrectal ultrasonography is recommended as a diagnostic tool for patients whose PSA level ranges from a detectable level to less than or equal to 2 ng/mL. Cancer 1995; 75:2153-8. Key words: prostate cancer, radiation therapy, biopsy, transrectal ultrasonography, prostate specific antigen.

The participating institutions of the American Cancer Society National Prostate Cancer Detection Project did 520 biopsies on 2425 men over a 3.5-year period. A total of 88 cancers were confirmed pathologically, 93% of which clinically were organ confined. In 324 men (62.3%), a recommendation for biopsy was made based solely on the results of transrectal ultrasonography (TRUS); in 69 patients (13.3%), solely on the digital rectal examination (DRE); in 116 patients (22.3%), on abnormal DRE and TRUS examinations; and in 11 patients (2.1%), in whom DRE and TRUS were normal, on elevated prostate-specific antigen (PSA) levels. The TRUS was abnormal in 80.6% of men found to have cancer, and the PSA level and DRE were abnormal for 67% and 50% of cancers, respectively. The influence of PSA level on cancer detection increased as the serum level increased above 4 ng/ml. The positive predictive values of both DRE and TRUS were influenced significantly by the presence of an elevated PSA level (P = 0.044 and P < 0.001, respectively). The results of this ongoing multicenter study support the following statements: (1) the prostate cancer detection rate is influenced by this diagnostic triad and (2) the detection rate of organ-confined disease can be improved substantially by early detection programs. Cancer 1992; 69:1195-1200.

The standard method of screening for prostate cancer is the digital rectal examination (DRE), in which the physician feels for abnormal masses in the prostate gland. In recent years, ultrasound imaging has been used in the detection of prostate cancer; the transrectal ultrasound (TRUS) imaging can detect smaller abnormal masses than a physician's finger. Both methods are far from satisfactory; biopsy will reveal actual prostate cancer in only about half of the patients with abnormal results on the screening. Over the last decade, the tumor marker PSA, or prostate-specific antigen, has grown in importance as a diagnostic indicator for prostate cancer. Increased amounts of PSA in the blood strongly suggest that prostate cancer may be present. A comparison of DRE, TRUS, and PSA was conducted in the evaluation of 124 patients undergoing a prostate biopsy. All patients required the biopsy on the basis or an abnormal DRE or TRUS examination. Forty-five percent of the patients were found to have prostate cancer. Only 17.5 percent of the patients with low levels of PSA (less than four nanograms per milliliter) ultimately proved to have cancer. Conversely, 83.3 percent of the patients with PSA levels higher than 20 nanograms per milliliter had cancer. Of the patients with intermediate PSA values, 68.7 percent had cancer. These results indicate that while patients with low PSA levels have lower risks of prostate cancer, the risk is not negligible. However, patients with high levels of PSA have a very high risk of cancer and such patients should invariably undergo prostate biopsy. (Consumer Summary produced by Reliance Medical Information, Inc.)