Main Session

Sep 29

PQA 06 - Genitourinary Cancer, Gynecological Cancer, and Health Care Access and Engagement

3268 - The Association between Disease Control and Novel Pathologic or Radiographic Risk Factors in Intermediate-Risk Prostate Cancer (IR-PCa)

02:15pm - 03:30pm ET

Poster Hall - Exhibit Hall A

Screen: 9

POSTER

Presenter(s)

Beck French, BA - The Ohio State University College of Medicine, Columbus, OH

B. M. French¹, E. Stamas², Y. Gokun³, T. Paul¹, S. J. Wang¹, and J. Eckstein¹; ¹Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH, ²The Ohio State University, Columbus, OH, ³Center for Biostatistics, Department of Biomedical Informatics, The Ohio State University Wexner Medical Center, Columbus, OH

Purpose/Objective(s): The AJCC PCa staging system, the NCCN risk stratification system, and resulting treatment paradigms do not incorporate MRI-based T staging or biopsy-detected high-risk features such as perineural invasion (PNI) and intraductal carcinoma (IDC-P). We evaluated whether MRI-detected extraprostatic extension (EPE) and seminal vesicle invasion (SVI) or biopsy-detected PNI/IDC-P were associated with disease control following definitive radiotherapy (RT), and whether ADT utilization modified outcomes in patients with IR-PCa demonstrating these features.

Materials/Methods: We retrospectively analyzed 177 patients with NCCN-defined IR-PCa treated with definitive RT between 2015 and 2020 at a tertiary academic institution. Patients were stratified by receipt of staging MRI prior to RT. MRI findings were categorized as: no risk factor (no EPE/SVI), any uncertain risk factor (indeterminate EPE and/or SVI based on MRI report), or any definitive risk factor (definitive EPE and/or SVI based on MRI report). Pathological features including PNI and IDC-P were identified from biopsy reports. Clinical endpoints included overall survival (OS), and PFS (defined as biochemical progression or biopsy-confirmed radiographic progression), which were estimated using Kaplan-Meier methods and compared using log-rank tests.

Results: Among 177 IR-PCa patients, 107 (60.5%) underwent staging MRI. Median follow-up was 72.0 months (range: 0.8–113.7 months). ADT utilization was similar among patients with vs without MRI (43% vs 45.7%; p=0.72). PFS events were uncommon (8/177 patients; 4.52%). Among patients with MRI, 76 (71.0%) had no risk factors, 26 (24.3%) had =1 uncertain risk factor without a definitive risk factor, and 5 (4.7%) had a definitive risk factor. Among 46 patients receiving ADT+RT, five-year PFS differed across MRI risk strata (100.0% no risk vs 93.3% uncertain risk vs 66.7% definitive risk; p=0.03), whereas no significant difference was observed by MRI risk strata among RT-alone patients (p=0.91).

PNI or IDC-P were present in 74 (42.0%) patients. PFS did not differ by PNI/IDC-P status (p=0.86) in the overall cohort (n=177). Five-year PFS did not significantly differ based upon the presence of PNI/IDC-P among 99 patients who received RT alone (p=0.69) or among the 77 patients who received RT+ADT (p=0.18), while five-year OS was worse (90.7%) among those with either PNI or IDC-P compared to those with neither PNI nor IDC-P (94.8%) among 99 RT-alone patients (p=0.03).

Conclusion: Adverse MRI findings were associated with shorter PFS in patients treated with RT+ADT but not those treated with RT alone. No association was found between PFS and PNI/IDC-P regardless of receipt of ADT. Future studies are needed to further explore the clinical implications of PNI, IDC-P, and MRI-detected SVI or EPE.