Association of multiparametric magnetic resonance imaging findings with oncologic outcomes in non-palpable localized prostate cancer.

Abstract

281 Background: Multiparametric magnetic resonance imaging (mpMRI) is becoming increasingly integrated into the evaluation and medical decision making for localized prostate cancer. However, mpMRI findings have not been correlated with prostate cancer outcomes and therefore are not currently included in staging. The purpose of this study was to test the association between mpMRI detected extraprostatic extension with oncologic outcomes in patients with non-palpable prostate cancer. Methods: We used the Veterans Affairs Prostate Data Core to identify patients diagnosed with cT1N0M0 prostate cancer between 2000-2021 with an mpMRI prior to definitive treatment. We reviewed MRI reports to identify presence of extracapsular extension (MRI-T3a), seminal vesicle invasion (MRI-T3b), and adjacent organ invasion (MRI-T4). We assessed the impact of mpMRI findings on metastasis free survival with multivariable Fine-Gray competing-risks regression. Results: Overall, 3,142 veterans with cT1N0M0 prostate cancer were included. There were 1,411 (45%) Black patients. By clinical staging, 904 (29%) had low risk, 1,626 (52%) had intermediate risk, and 612 (19%) had high risk disease. The majority of patients were treated with radiation (N=2,267; 72%). There were 217 (7%) patients with MRI-T3a disease, 87 (3%) patients with MRI-T3b disease, and 26 (1%) patients with MRI-T4 disease. The median follow-up time was 5.4 years (90% CI, 1-13 years). The 5-year cumulative incidence of metastases for patients with low, intermediate, and high risk prostate cancer were 3% (95% CI, 2-4%), 7% (95% CI, 6-8%), and 15% (95% CI, 12-18%). The 5-year cumulative incidence of metastases for patients with MRI-T3a, MRI-T3b, and MRI-T4 disease were 15% (95% CI, 10-20%), 29% (95% CI, 29-39%), and 40% (95% CI, 13-66%). After controlling for age, race, risk stratification (which includes prostate specific antigen (PSA) and grade group), local therapy, and co-morbidities, the presence of MRI-T3a (HR 1.58, 95% CI 1.09-2.29, p=0.02), MRI-T3b (HR 3.38, 95% CI 2.31-4.95, p<0.0001), and MRI-T4 disease (HR 4.47, 95% CI 2.32-8.62, p<0.0001) were independently associated with worse metastasis free survival. Similar results were obtained with PSA and grade group as individual variables. Conclusions: Extraprostatic extension observed on mpMRI is independently prognostic of metastasis free survival in patients with non-palpable prostate cancer. mpMRI is a critical imaging modality that should be widely available for patients with prostate cancer, and studies are ongoing to define its role as a standard staging modality.