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Background: Atypical small acinar proliferation (ASAP) is a diagnosis that occurs in about 1-2% of prostate biopsies. Approximately, 30-40% of patients with ASAP may develop prostate cancer. Current guidelines recommend a repeat biopsy within 3-6 months after the initial diagnosis. The adoption of active surveillance for low risk prostate cancer has reduced overtreatment by recommending repeat biopsy after one year of surveillance. Our objective was to determine if there is an association between ASAP and low risk prostate cancer, with no significant occurrence of skip lesions to high grade disease and thus, challenge the need for immediate repeat biopsy. We hypothesize that ASAP patients who develop low risk prostate cancer may be managed on active surveillance, with no increased risk of disease progression.
Methods: We performed a retrospective chart review that identified 108 patients who underwent prostate biopsy from 2000 to 2013 and obtained a diagnosis of ASAP. Patients underwent biopsies either for elevated PSAs or prostatic nodules found on digital rectal exam. These patients were followed with repeat biopsies and PSA evaluations. Prostate cancer detection, stage, and Gleason score were documented.
Results: Of the 96 patients with ASAP on initial diagnosis, 56 had a repeat biopsy, but only 45 were within 3-6 months. The remaining 12 were within 2.5 years. 21 patients went on to develop prostate cancer. Of those 21 patients, 17 had Gleason 3+3 disease and only 4 had Gleason 3+4 disease. Prostatectomy was performed on 9 patients, while 2 received radiation. One patient was upgraded from 3+3 to 3+4 on final pathology. No patients had a Gleason score of 4+3 or higher.
Conclusions: Our results demonstrate that a limited number of patients (37.5%) with an initial diagnosis of ASAP went on to develop prostate cancer if they had a repeat biopsy within 2.5 years. Of the 37.5% who progressed, 76.3% developed low risk prostate cancer defined by D’amico criteria. Significantly, no patients developed high risk disease following an initial diagnosis of ASAP. Based on this information we recommend that an ASAP diagnosis be managed with active surveillance. This would include PSA and DRE at 4-6 month intervals followed by a repeat biopsy at one year.