One of the eagerly anticipated prostate cancer phase III trials, NRG GU-005, was presented in the Plenary Session Monday, September 29, while earlier in the day James Yu, MD, MHS, FASTRO, Dartmouth-Hitchcock Medical Center, focused on the “Quality of Life (QOL) Results from NRG-GU005: A Phase III Trial of SBRT vs. Hypofractionated IMRT for Localized Intermediate Risk Prostate Cancer.” This superiority trial randomized 698 men to SBRT (36.25 Gy/5 fractions to the prostate +/- proximal seminal vesicles) compared to moderately hypofractionated IMRT (MH-IMRT) (70 Gy/28 or 60 Gy/20).
The EPIC-26 was used to measure QOL, focusing on the proportion of patients meeting established minimally clinically important difference (MCID) thresholds. Dr. Yu noted, “Two key features of this study are first, we used QOL as a co-primary endpoint, which has been demonstrated to be a more sensitive measure of the patient experience compared to physician reported toxicity, and for intermediate risk prostate cancer is considered to be equally as important as disease-free survival, which is typically excellent in this group. Second, we focused on the proportion of patients with meaningful changes in QOL instead of looking only at group mean values which can miss smaller groups of patients who experience clinically relevant differences.”
Urinary obstructive and bowel QOL changes at two years, co-primary endpoints of the study (with disease free survival) were presented in the Plenary. Dr. Yu’s presentation at the genitourinary cancers session focused on all QOL domains at one year with the domains not included in the primary analysis also presented at two years. The arms were well balanced, with no differences in baseline QOL. At one year after treatment there were similarly no differences in the percentage with MCD declines in either urinary domain or vitality/hormonal. However, at one year those treated with SBRT were less likely to have declines in bowel (33% SBRT v. 46% MH-IMRT, p=0.002) and sexual QOL (34% v. 44%, p=0.03). At two years, the difference in sexual QOL did not persist (43% v. 41%, p=0.67), while men treated with SBRT reported less clinically significant urinary incontinence (26% vs. 35%, p=0.02). On multivariate analysis MH-IMRT was associated with 2.9-fold increased risk in experiencing a decline in urinary incontinence score (p=0.0058). These differences in QOL were mirrored in the CTCAE toxicity with greater rates of Grade 3 urinary toxicity with MH-IMRT (2.5%) compared to SBRT (0.6%, p=0.04). Grade 3 rectal bleeding was rare and not significantly different between arms (0.6% SBRT v. 1.5% MH-IMRT) but including grades 1-3 revealed less bleeding with SBRT (11% v. 17%, p=0.01).
The investigators and patients should be congratulated, as NRG GU-005 is a critical piece in our understanding of SBRT for prostate cancer. These QOL data provide clinically useful information, although currently the results at only two years are too short to make meaningful conclusions about long-term outcomes. Nevertheless, all signals presented here suggest SBRT is safe and indeed potentially has less toxicity and QOL declines than MH-IMRT.
Abstract 193 - Quality of Life (QOL) Results from NRG-GU005: A Phase III Trial of SBRT vs. Hypofractionated IMRT for Localized Intermediate Risk Prostate Cancer was presented in SS 16 – GU 4: Quality of Life Outcomes after Prostate Radiotherapy during ASTRO’s 67th Annual Meeting.
Read additional commentary from Dr. Hamstra on the NRG: GU005 secondary QOL results.
