Introduction:

Atypical Small Acinar Proliferation (ASAP) is a lesion found on prostate biopsy that may increase the risk for diagnosing clinically significant prostate cancer (CSPC) on repeat biopsy. Current AUA guidelines recommend additional testing in patients diagnosed with ASAP, however, outcomes of diagnosis of CSPC after incorporating additional testing modalities such as multiparametric MRI (mpMRI) remain unclear. Additionally, it is unclear whether a repeat prostate biopsy should be obtained in the setting of these lesions.  This study’s objective was to investigate whether mpMRI can obviate the need for repeat prostate biopsy in those diagnosed with ASAP.

Methods:

This study was a retrospective review of all patients at our institution diagnosed with ASAP from the years 2014-2023. ASAP was initially detected on standard 12-core systematic prostate biopsy performed by a urologist as part of workup for elevated PSA. In these patients, our institution’s protocol during this period was to obtain mpMRI within 6 months and repeat biopsy within one year in any man with a first-time diagnosis of ASAP. Patients with a positive MRI (PIRADS 3 or greater) underwent a targeted biopsy of the lesion for repeat biopsy. Patients with known prostate cancer or co-diagnosis of prostate cancer on biopsy were excluded from review.  Clinical data including demographics, PSA, biopsy data, and mpMRI PIRADS scores were collected retrospectively from the medical record. CSPC was defined as Gleason Grade Group 2 or higher on biopsy. Rates of CPSC diagnosis were assessed relative to mpMRI findings.

Results:

A total of 75 patients with a first-time diagnosis of ASAP who underwent repeat biopsy within one year of initial diagnosis were identified. In all patients with a new diagnosis of ASAP, the likelihood of finding CSPC on repeat biopsy was 13.3% (10/75). In all patients with a new diagnosis of ASAP, 47 (62.7%) underwent MRI for further workup. For patients with a negative MRI (PIRADS 2 or less), the likelihood of finding CSPC was 6.3% (2/32). Positive MRI (PRIADS 3 or greater) had a 40% (6/15) chance of having CSPC on re-biopsy. At our institution in the setting of a new diagnosis of ASAP, the negative predictive value of mpMRI (PIRADS 2 or less) was 93.6%.  

Conclusion:

When mpMRI was performed after a new diagnosis of ASAP, only 6.3% of patients had CSPC in the setting of a PI-RADS 2 or lower lesion, while 40% had CSPC in the setting of PI-RADS 3 or higher lesions. These findings suggest that mpMRI is an appropriate tool to triage patients with a new diagnosis of ASAP. Clinicians may consider forgoing repeat prostate biopsy in the setting of a new diagnosis of ASAP.

Funding: N/A