Validation of the NCCN Subclassification for Intermediate‐Risk Prostate Cancer in a Japanese Radical Prostatectomy Cohort: Results From the MICAN Study

OBJECTIVES: We aimed to evaluate the prognostic utility of subclassifying patients with intermediate-risk prostate cancer into favorable and unfavorable subgroups in a large Japanese cohort undergoing radical prostatectomy, focusing on adverse pathology and oncologic outcomes. METHODS: We retrospectively analyzed 1485 intermediate-risk patients from the MICAN (Medical Investigation Cancer Network) study registry who underwent radical prostatectomy between 2010 and 2020 in Ehime Prefecture, Japan. Patients were categorized into favorable or unfavorable intermediate-risk groups based on the National Comprehensive Cancer Network (NCCN) guideline. We examined up-grading, up-staging, and adverse pathology defined as pathological ≥T3, grade group ≥ 4, or lymph node involvement. Kaplan-Meier analysis was used to evaluate prostate-specific antigen (PSA) failure-free survival and overall survival. RESULTS: Among 1485 patients, 590 (40.2%) were classified as having favorable intermediate risk and 879 (59.8%) as having unfavorable intermediate risk. Up-grading and up-staging were observed more frequently in the unfavorable group. Adverse pathology was more frequent in the unfavorable group (64.8%) than that in the favorable group (39.4%) (p < 0.001). The 5-year PSA failure-free survival rates were 92.1% for the favorable group and 80.1% for the unfavorable group (p < 0.001). Although the 5-year overall survival rate did not reach statistical significance (98.4% vs. 97.9%, p = 0.085), the favorable group showed a trend toward better survival. CONCLUSIONS: The subclassification of intermediate-risk prostate cancer into favorable and unfavorable groups is prognostically meaningful in Japanese patients undergoing radical prostatectomy. Higher rates of adverse pathological findings and inferior PSA failure-free survival in the unfavorable group support the clinical utility of this subclassification.