Genitourinary Cancer

PV QA 1 - Poster Viewing Q&A 1

SU_25_2257 - Application of a Prognostic Stratification System for High-Risk Prostate Cancer to Patients Treated With Radiation Therapy: Implications for Treatment Optimization

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Application of a Prognostic Stratification System for High-Risk Prostate Cancer to Patients Treated With Radiation Therapy: Implications for Treatment Optimization
B. Foster1, W. C. Jackson2, C. C. Foster3, R. T. Dess2, E. I. Abu-Isa2, P. W. McLaughlin2, G. S. Merrick4, J. W. D. Hearn2, D. E. Spratt2, S. Liauw3, and D. A. Hamstra5; 1Tufts Medical Center, Department of Radiation Oncology, Boston, MA, 2Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 3The University of Chicago, Department of Radiation and Cellular Oncology, Chicago, IL, 4Schiffler Cancer Center, Wheeling, WV, 5Oakland University William Beaumont School of Medicine, Department of Radiation Oncology, Dearborn, MI

Purpose/Objective(s): We applied an established prognostic model to high-risk prostate cancer (HRPC) patients undergoing definitive radiotherapy (RT) and hypothesized treatment variables including brachytherapy boost or androgen deprivation therapy (ADT) would differentially impact the resulting clinically-defined subgroups.

Materials/Methods: One thousand seventy-five HRPC patients undergoing definitive RT between 1995-2010 were reviewed. Median follow-up was 62.3 months. They received either dose-escalated external beam radiotherapy (n = 628; EBRT, >=75 Gray) or combined-modality radiotherapy (n = 447; pelvic radiotherapy and low-dose rate brachytherapy boost, CMRT). 82.9% received ADT. Men were stratified into previously-reported groups: (1) good-prognosis with 1 high-risk feature (PSA >20 ng/mL, Gleason score [GS] 8-10, cT3-T4); (2) intermediate-prognosis with PSA >20 ng/mL + cT3-T4 but GS < 8; and (3) poor-prognosis (PP) with GS 8-10 + another high-risk feature. Kaplan-Meier methods and Cox proportional hazards regression assessed biochemical failure (BF), distant metastasis (DM), prostate cancer-specific mortality (PCSM) and overall mortality (OM). C-indices assessed the 3-compartment model and a 4-compartment model adding an additional point for GS 9-10.

Results: The 3-compartment model was prognostic for all endpoints (p<0.0001 BF, DM and PCSM; p=0.019 OM). C-indices for BF, DM, PCSM and OM were 0.62, 0.64, 0.61 and 0.57. On multivariate analysis, CMRT and longer-duration ADT (>=24 months) were associated with improved BF, DM, and PCSM. CMRT was associated with improved OM (p<0.0001, Table 1). GS 9-10 was the strongest predictor of PCSM. C-indices for BF, DM, PCSM, and OM using the 4-compartment model were 0.62, 0.65, 0.68, and 0.56, respectively. In PP patients, CMRT + LTADT (>12 months) had low 10-year PCSM (3.7% ± 3.6%) when compared to 25.8% ± 9.2% with EBRT + LTADT.
Table 1: Multivariate Analysis of Risk Groups, GS 9-10 and Treatment Variables (n=1075)
BF DM PCSM OM
HR p HR p HR p HR p
Intermediate group 2.1 0.003 2.2 0.023 1.8 0.18 0.6 0.082
Poor group 3.0 <0.0001 3.4 <0.0001 2.4 0.0011 1.1 0.44
0.1-12.0 months ADT 0.5 0.002 0.5 0.0030 0.6 0.07 0.8 0.3
12.1-24 months ADT 0.7 0.15 0.6 0.14 0.8 0.6 1.1 0.8
>24 months ADT 0.3 <0.0001 0.2 <0.0001 0.4 0.006 0.8 0.22
CMRT 0.3 <0.0001 0.4 <0.0001 0.4 0.0006 0.4 <0.0001
GS 9-10 1.2 0.25 1.7 0.02 3.2 <0.0001 1.7 <0.0001

Conclusion: The prognostic model applies to high-risk RT men. GS 9-10 is a powerful predictor of PCSM even within this model, and its incorporation into a novel 4-compartment stratification improved prognostication of DM and PCSM. Among PP patients, CMRT + LTADT yields encouraging 10-year PCSM outcomes compared to EBRT + LTADT. These findings suggest longer-duration ADT in combination with brachytherapy boost may be beneficial even for a particularly high-risk subgroup.

Author Disclosure: B. Foster: None. W.C. Jackson: None. C.C. Foster: None. P.W. McLaughlin: None. J.W. Hearn: None. S. Liauw: None. D.A. Hamstra: Consultant; Augmenix. Advisory Board; Genome DX.

Send Email for Benjamin Foster


Assets

SU_25_2257 - Application of a Prognostic Stratification System for High-Risk Prostate Cancer to Patients Treated With Radiation Therapy: Implications for Treatment Optimization



Attendees who have favorited this

Please enter your access key

The asset you are trying to access is locked. Please enter your access key to unlock.

Send Email for Application of a Prognostic Stratification System for High-Risk Prostate Cancer to Patients Treated With Radiation Therapy: Implications for Treatment Optimization