M. P. Dykstra1, S. N. Regan1, H. Yin1,2, W. McLaughlin1,3, M. Zaki4, M. Mislmani5, S. R. Miller II6, V. Narayana1,3, D. Kendrick7, M. Khadija8, D. A. Dryden4, D. W. Litzenberg1, M. Mietzel1, D. K. Heimburger9, M. Schipper1,2, W. C. Jackson1, and R. T. Dess1; 1Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 2Department of Biostatistics, University of Michigan, Ann Arbor, MI, 3Department of Radiation Oncology, Assarian Cancer Center, Ascension Providence Hospital, Novi, MI, 4Covenant HealthCare, Saginaw, MI, 5West Michigan Cancer Center, Kalamazoo, MI, 6Department of Radiation Oncology, Wayne State University School of Medicine, Detroit, MI, 7Michigan Radiation Oncology Quality Consortium Coordinating Center, Ann Arbor, MI, 8University of Michigan Health West, Wyoming, MI, 9Munson Healthcare, Traverse City, MI
Purpose/Objective(s): Recent individual patient meta-analysis confirms the overall survival benefit of long-term androgen deprivation therapy (ADT) when added to definitive radiotherapy for men with locally advanced prostate cancer. Moreover, based on data from STAMPEDE, androgen receptor signaling inhibitors (ARSI) are recommended for select patients with multiple higher-risk features or clinically node positive (cN1) disease. Given these developments, it is important to understand ADT treatment intent in the modern era. We sought to characterize practice patterns across diverse practices within a statewide radiation oncology quality consortium. Materials/
Methods: We evaluated patients enrolled in the consortium with intact, non-metastatic, high-risk or cN1 disease. Patient, tumor, and treatment data were prospectively collected using standardized data elements. Physicians prospectively documented intent, type, and duration of ADT. The primary outcome was guideline-concordant intended ADT use of =18 months per NCCN. Secondary analyses included ARSI use among men meeting STAMPEDE high-risk M0/N1 criteria. Multivariable analysis (MVA) was used to determine associations with patient and facility-level factors. A mixed model with site level random intercept was used to test for facility-level variation beyond that explained by patient characteristics and to estimate ADT utilization rates for each site if that site had treated the entire cohort. Results: Between 6/9/20 to 1/31/24, 422 men with intact high risk prostate cancer were identified across 24 centers. Most (95.3%, n = 402/422) received dose-escalated radiotherapy (EQD2 =74Gy (a/b = 1.5)). cT3/4 disease was present in 8.5%, and 13.7% (n=55/422) had cN1 disease. Most men had grade group 4 (42.2%, n=178/422) or 5 (31.5%, n=133/422) adenocarcinoma. ADT use =18 months was planned for 50.9% (n=215/422), <18 months in 34.5% (n=146/422), and no ADT was intended for 14.4% (n=61/422). On MVA, grade group 5 vs =3, PSA =40, =50% positive biopsy cores, and cN1 were significantly associated with guideline-concordant ADT. There was significant variation (p<0.001) in intended guideline-concordant ADT use by facility, with predicted probability by center ranging from 20.2% to 85.5%. STAMPEDE M0/cN1 criteria were met for 18.6% (n=83/446) and intended ARSI use in this subset was 28.9% (n=24/83), which increased after publication of STAMPEDE M0/N1 (n = 23/71 [32.4%] vs 1/11 [9%], p < 0.01). Conclusion: Guideline concordant intended ADT use in a modern, multi-institutional high risk prostate cancer cohort was 50.9%. Longer ADT use was associated with higher risk tumor features but had persistent facility-level heterogeneity. Fewer than 1 in 5 met STAMPEDE high-risk M0/N1 criteria, and ARSI use among these men was <50%. Further efforts are needed to improve uptake of guideline-concordant therapies with known survival benefits.
