Integrating Apparent Diffusion Coefficient and Prostate-Specific Antigen as Prognostic Factors of Treatment Response to Androgen Deprivation Therapy and Radiotherapy in Prostate Cancer.

This study evaluates the combined prognostic value of the apparent diffusion coefficient (ADC) from multiparametric MRI (mpMRI) and prostate-specific antigen (PSA) levels at 6 months post-radiotherapy (RT) in assessing treatment response in prostate cancer patients treated with RT and androgen deprivation therapy (ADT). All prostate cancer patients classified as unfavorable intermediate-risk, high-risk, or very high-risk, according to NCCN criteria, who received ADT and RT between 2008 and 2019 and underwent mpMRI and PSA testing 6 months after RT were included. Patients were stratified into three profiles based on threshold PSA (≤ vs. >0.1 ng/mL) levels and ADC (≤ vs. >1.24 × 10 mm/s) values: Profile A: low PSA and high ADC; Profile B: either high PSA/high ADC or low ADC/low PSA; Profile C: high PSA and low ADC. Ten-year progression-free survival (PFS) and metastasis-free survival (MFS) were analyzed using Kaplan-Meier curves and multivariate Cox regression. Ninety-eight consecutive patients were retrospectively analyzed, of which 73 (74.5%) were high-risk. After a mean follow-up of 95.3 months, 19 (19.39%) patients progressed. Ten-year PFS, MFS, and overall survival were 75.6%, 87%, and 89.5% respectively. Progression events were 9.1% (Profile A), 29.4% (Profile B), and 44.4% (Profile C). Eight-year PFS was 89.2% (profile A), 70.9% (profile B) HR: 3.021 (CI 95%: 1.031-8.849; = 0.044) and 44.4% (profile C) HR: 6.145 (CI 95%: 1.645-22.955; = 0.007). Multivariate analysis confirmed a higher risk of progression in patients from profile B with HR: 3.958 (CI 95%: 1.18-13.191; = 0.025) and profile C with HR: 41.945 (CI 95%: 5.000-351.761; < 0.001) compared to patients from profile A. Metastasis events were 5.5% (Profile A), 8.8% (Profile B), and 33.3% (Profile C). Eight-year MFS was 100% (profile A), 89.6% (profile B) HR: 1.373 (CI 95%: 0.277-6.811; = 0.689), and 74.1% (profile C) HR: 5.566 (CI 95%: 1.119-27.692; = 0.047). The integration of PSA response and ADC measures at 6 months post-RT provides an effective combined prognostic factor to identify patients at higher risk of relapse, supporting closer monitoring and potential treatment intensification.