Genitourinary Cancer

SS 28 - GU 3 - New Insights Into Treatment Intensification Strategies for Prostate Cancer

199 - International Multicenter Validation of an Intermediate-Risk Subclassification of Men Treated With Radical Treatment Without Hormone Therapy

Tuesday, October 23
2:45 PM - 2:55 PM
Location: Room 007 A/B

International Multicenter Validation of an Intermediate-Risk Subclassification of Men Treated With Radical Treatment Without Hormone Therapy
A. Berlin1,2, F. Y. Moraes1,2, A. Koven3, N. S. Salgado1,2, H. Jiang4, R. Glicksman1,2, E. T. T. Leite5, J. L. F. Silva5, R. Gadia5, N. E. Fleshner6, P. Chung1,2, C. N. Catton1,2, Z. S. Zumsteg7, T. M. Morgan8, J. W. D. Hearn9, R. Mehra10, R. T. Dess9, F. Y. Feng11, A. Finelli6, and D. E. Spratt9; 1Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada, 2Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada, 3Faculty of Medicine, University of Toronto, Toronto, ON, Canada, 4Department of Biostatistics, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada, 5Hospital Sirio-Libanes, São Paulo, Brazil, 6Department of Surgical Oncology, Division of Urology, Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, Canada, 7Cedars-Sinai Medical Center, Los Angeles, CA, 8Department of Urology, University of Michigan, Ann Arbor, MI, 9Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 10Department of Pathology, University of Michigan, Ann Arbor, MI, 11UCSF Department of Urology, San Francisco, CA

Purpose/Objective(s): National Comprehensive Cancer Network guidelines have recently endorsed the Memorial Sloan Kettering (MSK) subclassification of intermediate-risk prostate cancer into favorable (FIR) and unfavorable (UIR) subgroups. These subgroups are often used for decision-making regarding the addition of hormone therapy. However, the subclassification was developed in a heterogeneous cohort of men, many of which received androgen deprivation therapy (ADT), and thus the natural history of hormone therapy naïve FIR and UIR men remains unknown. Herein, we perform the first multi-center validation study across all forms of radical therapy in men with intermediate-risk prostate cancer who did not receive combined hormone therapy.

Materials/Methods: After receiving institutional review board approval from three academic centers, intermediate-risk men treated with radical monotherapy (dose escalated external beam radiation therapy (DE-EBRT), brachytherapy (BT) as monotherapy, or radical prostatectomy (RP)) without the addition of ADT were included. UIR prostate cancer was defined as any intermediate-risk patient with a primary Gleason pattern of 4, percentage of positive biopsy cores ≥ 50%, or multiple intermediate-risk factors (cT2b-c, prostate-specific antigen 10-20 ng/mL, or Gleason score 7). Cumulative incidence curves with competing risk analyses were performed for distant metastasis (DM) and prostate cancer-specific mortality (PCSM).

Results: A total of 2550 intermediate risk men (1044 FIR and 1506 UIR) were included, of which 1149 had RP, 1143 had DE-EBRT, and 258 had BT. The median follow-up for the RP, DE-EBRT, and BT cohorts were 60.4, 70.6, 107.4,months respectively. The 10-year cumulative incidence of DM for FIR vs UIR were 0.6% (95%CI:0.6-0.6) vs. 10.4% (95%CI:6.5-14.3) for RP (p<0.001), 3.4% (95%CI:1.4-5.4) vs. 13.2% (95%CI:9.3-17.1) for DE-EBRT (p<0.001), and 4.4% (95%CI:0.5-8.3) vs. 12.4(95%CI:2.6-22.2) for BT (p=0.025). The 10-year rates for PCSM for FIR vs UIR were 0% (95%CI:0-0) vs. 3.4% (95%CI:1.4-5.4) for RP (p=0.031), 1.3% (95%CI:0-3.3) vs. 5.2% (95%CI:3.2-7.2) for DE-EBRT (p=0.049), and 0.6 (95%CI:0-2.6) vs. 3.0% (95%CI:0-6.9) for BT (p=0.028).

Conclusion: This multicenter international effort has independently validated the prognostic value of the MSK intermediate-risk subgroup classification in men who are hormone therapy naïve across all radical treatment modalities. Our data demonstrates that the current definition of FIR may not be ideal as 3-4% of men still develop distant metastasis at 10 years even with definitive therapy. These results underscore the need for other biomarkers to improve risk stratification, such as the recently reported clinical-genomic risk group classification, and the necessity of studying the differential impact of treatment intensification strategies, such as ADT, among these subgroups.

Author Disclosure: A. Berlin: None. A. Koven: None. N.S. Salgado: None. E.T. Leite: None. N.E. Fleshner: None. P. Chung: Research Grant; Sanofi. C.N. Catton: Research Grant; AbbVie Corporation. Advisory Board; AbbVie Corporation, Bayer Corporation, Estellas Corporation. Chair of Sarcoma Services Committe; CancerCare Ontario. T.M. Morgan: None. F.Y. Feng: Research Grant; GenomeDx. Advisory Board; GenomeDx, Dendreon, Sanofi. Travel Expenses; GenomeDx. Liaison, GU Translational Research Program; Radiation Therapy Oncology Group. President and Founder; PFS Genomics.

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