The prognostic relevance of high-grade prostatic intraepithelial neoplasia (HGPIN) and atypical small acinar proliferation (ASAP) in men with Grade Group (GG) 1 prostate cancer (PCa) remains unclear. This study aimed to assess and compare the risk of progression to clinically significant PCa (GG≥2) among patients with isolated HGPIN/ASAP and those with GG1 disease, either with or without concomitant HGPIN/ASAP.
Patients diagnosed between 2017 and 2023 were identified from our prospectively maintained institutional registry and stratified into three groups based on MRI-guided diagnostic biopsy findings: (1) isolated HGPIN/ASAP without cancer (n=210), (2) GG1 PCa without HGPIN/ASAP (n=97), and (3) GG1 PCa with concomitant HGPIN/ASAP (n=41). All patients who underwent a follow-up MRI-guided biopsy were analyzed for disease upgrading to GG≥2. Both diagnostic and follow-up biopsies were MRI-guided. Baseline characteristics and progression rates were compared between groups.
A total of 196/348 (56%) patients received a follow-up biopsy: 85/210 (40.5%) in group 1, 95/97 (97.9%) in group 2, and 16/41 (39%) in group 3. Baseline variables, including age, family history, PSA, PSA density, DRE findings, MRI results and stage, and interval between biopsies, were similar across groups (p>0.05). Progression to GG≥2 was observed in 43/85 (50.6%), 36/95 (37.9%), and 10/16 (62.5%) cases in groups 1, 2, and 3, respectively (overall p=0.083,Figure 1). Compared individually, isolated HGPIN/ASAP showed a borderline higher risk of progression than GG1 PCa alone (50.6% vs 37.9%, OR 1.67, p=0.099), suggesting that these lesions may not be biologically indolent. Patients with GG1 PCa and concomitant HGPIN/ASAP exhibited an even greater, though statistically non-significant, risk (OR 2.71, 95% CI 0.81–9.88, p=0.098), likely influenced by the limited cohort size (n=16).
A progression risk comparable to—or even higher than—that of GG1 disease (50.6% vs 37.9%) is demonstrated by isolated HGPIN/ASAP, indicating that close clinical surveillance is warranted. In GG1 patients, the presence of concomitant HGPIN/ASAP is associated with a substantial increase in progression risk to 62.5%, and should be regarded as a high-risk feature requiring intensified monitoring or an early repeat biopsy during active surveillance.
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