ASCO GU 2018: Improving risk-stratification of localized prostate cancer in a prospective active surveillance cohort

San Francisco, CA ( Dr. Justin Gregg and colleagues presented their work on active surveillance (AS) for prostate cancer, specifically assessing improved risk-stratification. Despite the appropriate adoption of AS in men with low and intermediate risk prostate cancer, there is no consensus regarding an optimal monitoring scheme. The objective of this study was to examine predictors of disease reclassification in a prospective single-institution AS cohort.

For this study (2006-2015), the authors utilized an AS cohort of 803 patients that met inclusion criteria. These were men with localized prostate cancer diagnosed within 6 months of AS enrollment who were then stratified into four groups. Group 1 was defined by a Gleason score ≤6 (3+3), one positive core (< 3 mm), and a PSA level < 4 ng/mL (adjusted by prostate size). Group IIa was classified as Gleason 6, one positive core, and either tumor length ≥3 mm or PSA ≥4 ng/mL. Group IIb included men with Gleason 6, > one positive core, and any PSA level or tumor length. Finally, Group IIc consisted of Gleason 7, > one positive core or any PSA. Monitoring included PSA and digital rectal exam every 6 months. A prostate biopsy was repeated at 1 year and then on a predetermined biopsy scheme. Patients with reclassified disease (upgrading, increase in positive cores and/or tumor length) were offered treatment. The authors used Cox proportional hazards modeling to determine the association of baseline clinicopathologic parameters with time to reclassification.

Among the 803 men included, there were 242 group I patients, 67 group IIa, 376 group IIb, and 118 group IIc. The median age was 64 years (range 36–83), there were 662 (82.4%) white men, 703 (87.5%) had cT1c disease, and 687 (85.6%) had Gleason 6 prostate cancer. The median PSA level was 4.2 ng/mL (range 0.2–34). At a median 2.9 years of follow-up, 249 (31.0%) men had disease reclassification and 258 (32.1%) men terminated AS to pursue curative treatment. Overall, 82% of reclassifications occurred within 3 years of study enrollment. Stratification to group IIb/IIc was significantly associated with time to reclassification compared to group I/IIa (HR 2.13, 95%CI 1.63-2.80), while CAPRA score did not show a significant difference (p = 0.27) in time to reclassification.

The authors concluded that grouping patients based on characteristics including tumor length and positive core number may improve risk stratification for AS in localized prostate cancer. However, even with these current findings, risk-based surveillance protocols merit further evaluation in larger cohorts. 

Presented by: Justin Gregg, MD Anderson Cancer Center, Houston, TX

Co-Authors: Chad A. Reichard, Xuemei Wang, Brian Francis Chapin, Louis L. Pisters, Curtis Alvin Pettaway, John Francis Ward, Mary F. Achim, Seungtaek Choi, Deborah A. Kuban, John W. Davis, Jeri Kim

Written By: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA