2196: Comparison of Two Types of Biochemical Failures Within the ASTRO and Phoenix Consensus Definitions in Patients Treated on RTOG 92–02 and 94–13

Abstract

A small, but significant population of prostate cancer patients treated with external beam radiation that are classified as biochemical failures by the ASTRO Consensus Definition or the new Phoenix Consensus Definition may be those patients who were deemed failures due to the “start of any salvage hormonal therapy.” Some of these patients’ PSA patterns following radiation are clinically obvious to be immediately considered failures, while other patients’ non-PSA clinical data may induce the start of hormonal therapy. “Start of hormonal therapy” failure patients may have a different prognosis compared to those patients who were deemed failures due to “three consecutive rising PSAs.” Additionally, this group may provide some insight into extreme PSA patterns. With current work on an updated Consensus definition progressing, this group should be explored. The next Consensus definition should be able to identify these patients in addition to the mainstream patients. We conducted this study to determine the differences in outcome between those patients who failed due to “start of any salvage hormonal therapy” and those patients who failed due to ASTRO or Phoenix PSA criteria. 2,800 patients from RTOG 92–02 (1,521) and 94–13 (1,279) were analyzed. The ASTRO consensus definition defines biochemical failure as occurring after three consecutive PSA rises following a nadir (A1), or any non-A1 event that prompted the initiation of salvage therapy (A2) after the end of radiation therapy. The date of failure is defined as the point half way between the nadir date and the first rise for A1, or the start date of salvage hormone therapy before the three consecutive rises for A2. The Phoenix definition defines biochemical failure as occurring when PSA is greater than nadir + 2 ng/ml (P1), or any non-P1 event that prompted the initiation of salvage therapy (P2) after the end of radiation therapy. The date of failure was defined to be the date that PSA is greater than nadir + 2 ng/ml for P1, or the start date of salvage hormone therapy before PSA is greater than nadir + 2 ng/ml for P2. Time to biochemical failure is measured from the randomization date to the date of failure. The median time to biochemical failure for all patients, by biochemical failure type, was 24.0 months for A1, 21.5 months for A2, 34.5 months for P1, and 24.9 months for P2. Patients classified as A2 failures had a trend of earlier median time to failure compared to A1, and patients classified as P2 failures had a significantly earlier median time to failure in all arms of both studies than those classified as P1. 81 of 291 (27.8%) patients originally classified as A2 were captured as biochemical failure by PSA rise (P1). Overall survival, disease specific survival, and PSA kinetics for A1, A2, P1, and P2 will be reported. Patients deemed biochemical failures by A2 or P2 may have biologically more aggressive disease. Further investigation of this group’s PSA kinetics is warranted. While the Phoenix consensus definition can capture additional patients previously not deemed A1 failures by the previous ASTRO consensus definition, a large portion of A2 are still not captured with the nadir + 2ng/ml used in P1. Future use of Phoenix consensus definition should report the P2 group outcomes separately.