Impact of pre-treatment MRI capsular involvement and extraprostatic extension on metastasis free and overall survival in localized prostate cancer

Background: Multiparametric magnetic resonance imaging (mpMRI) is not currently included in prostate cancer (PC) staging. The purpose of this study was to test the association between mpMRI detected prostate capsule involvement and extraprostatic extension (EPE) with metastasis free survival (MFS) and overall survival (OS) in patients treated for localized PC. Methods: Patients treated for localized PC between 2000-2021 from the Veterans Affairs Prostate Data Core having an mpMRI prior to definitive treatment were identified. MRI reports were assessed for minor or significant capsule abutment (defined as greater than or equal to 1.5 cm of capsule contact or radiologist’s mention of long segment abutment), extracapsular extension (ECE), seminal vesicle invasion (SVI), or adjacent organ invasion (OI). mpMRI findings’ impact on MFS by multivariable Fine-Gray competing-risks regression and OS by Cox regression were assessed. Results: Overall, 2,933 patients were included. Most pretreatment mpMRIs (85%) occurred after 2016. 1,238 (42%) patients were Black. 569 (19%) patients had palpable disease. Median follow-up was 5 years. The 5-year cumulative incidence of metastasis was 10% (95% confidence interval (CI) 9-11%) and death was 7% (95% CI 6-9%). There were 643 (22%) patients with minor capsule abutment, 212 (7%) with significant capsule abutment, 281 (10%) with ECE, 103 (4%) with SVI, and 25 (1%) with OI. After controlling for age, race, prostate specific antigen level, grade group, clinical tumor stage, and treatment, the presence of significant capsule abutment, ECE, SVI, and OI were independently associated with MFS, but minor capsule abutment was not. On multivariable analysis controlling for the same factors, EPE (ECE, SVI, or OI) was associated with worse OS. Conclusions: In a modern, real-world cohort of localized PC patients from the largest integrated health system in the United States, significant capsule abutment and EPE on mpMRI are independently prognostic of MFS, but minor capsular abutment is not. EPE is associated with inferior OS. Given its independent prognostic value for MFS and association with OS, mpMRI should be more widely available to PC patients. Studies are ongoing to define its role as a standard staging tool. Research Sponsor: None.

Duke Scholars

Author Joseph Kamel Salama Radiation Oncology

Author Rajan Tilak Gupta Radiology, Abdominal Imaging