LBA 10 - Two-year toxicity outcomes from PACE-C: Stereotactic Body Radiotherapy (SBRT) versus moderate hypofractionated radiotherapy (MHRT)
Presenter(s)
R. Ratnakumaran1,2, V. Hinder2, A. Chan3, S. Tolan4, P. Ostler5, H. Van Der Voet6, O. Naismith1,7, S. Jain8, A. Martin9, D. Price10, B. O'Neil11,12, A. Duffton13, J. Staffurth14, G. Sasso15,16, J. Pugh2, G. Manning2, S. Brown2, N. van As1,2, E. Hall2, and A. Tree1,2; 1The Royal Marsden NHS Foundation Trust, London, United Kingdom, 2The Institute of Cancer Research, London, United Kingdom, 3University Hospitals Coventry and Warwickshire, Coventry, United Kingdom, 4The Clatterbridge Cancer Centre, Liverpool, United Kingdom, 5Mount Vernon Cancer Centre, Northwood, United Kingdom, 6The James Cook University Hospital, Middlesbrough, United Kingdom, 7Radiotherapy Trials Quality Assurance Group, London, United Kingdom, 8Queen's University Belfast, Belfast, United Kingdom, 9Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom, 10Independent Patient and Public Representative, London, United Kingdom, 11St Luke’s Radiation Oncology Network, St Lukes Hospital, Dublin, Ireland, 12Cancer Trials Ireland, Dublin, Ireland, 13The Beatson West of Scotland Cancer Centre, Glasgow, United Kingdom, 14Cardiff University, Cardiff, United Kingdom, 15Auckland City Hospital, Auckland, New Zealand, 16Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
Purpose/Objective(s):
The PACE-B trial established SBRT as a standard of care for low- and favourable intermediate-risk localised prostate cancer. PACE-C aims to demonstrate non-inferiority of SBRT compared to MHRT in intermediate- or high-risk localised prostate cancer patients receiving androgen deprivation therapy (ADT). Here, we present late toxicity outcomes (up to 2 years after treatment) for the PACE-C trial.Materials/Methods:
1208 men with localised prostate cancer (stage T1c-T3a, = Gleason 4+4, PSA = 30ng/mL) were randomised (1:1) to SBRT (36.25 Gy in 5 fractions over 1–2 weeks) or MHRT (60 Gy in 20 fractions over 4 weeks), with 6–12 months of planned ADT. Late toxicity was assessed using RTOG and CTCAE at 6, 9, 12, 18, and 24 months. Co-primary late toxicity endpoints were the incidence of grade 2 or higher (G2+) gastrointestinal (GI) and genitourinary (GU) RTOG toxicities at 2 years. Secondary outcomes were CTCAE incidence and RTOG/CTCAE cumulative incidence (Kaplan-Meier) of G2+ GI/GU toxicities at 2 years, and the proportion of patients with a minimally clinically important difference (MCID) in EPIC-26 urinary incontinence (UI) (8 points), urinary irritative/obstructive (UO) (6 points) and bowel function (5 points) scores at 2 years. Comparisons were by treatment received, with proportions compared by chi-squared test. Significance level was 0.025 for co-primary and 0.01 for other endpoints.Results:
Baseline characteristics were similar between the SBRT (584 treated / 607 allocated) and MHRT (608 / 601) groups. Median age was 73.1 vs 72.4 years; intermediate-risk disease (NCCN criteria) was present in 65% vs 63%, and high-risk in 35% vs 37%; median PSA was 8.5 ng/mL vs 8.3 ng/mL. Late toxicity data were available for 584 SBRT and 604 MHRT patients. At two years, RTOG G2+ GU toxicity was higher with SBRT vs MHRT (9% (46/536) vs 3% (14/555), p<0.0001), as was CTCAE G2+ GU toxicity (13% (70/544) vs 4% (20/560), p<0.0001). Cumulative RTOG/CTCAE G2+ GU incidence was 24% (135/583) / 32% (184/583) for SBRT and 10% (57/602) / 13% (77/602) for MHRT. GI toxicity at two years was similar between SBRT and MHRT: RTOG G2+ GI toxicity (2% (9/537) vs 2% (11/557), p=0.71), and CTCAE G2+ GI toxicity (3% (19/544) vs 3% (17/560), p=0.67). Cumulative RTOG/CTCAE G2+ GI incidence was 8% (48/582) /13% (75/582) for SBRT and 6% (33/601) / 10% (60/602) for MHRT. G3+ GI and GU toxicities at two years were <2% for both groups. MCID in UO at two years was significantly higher with SBRT vs MHRT (46% (191/418) vs 27% (120/447), p<0.0001), though no significant difference was seen in UI (32% (144/445) vs 25% (117/470), p=0.012) or bowel function (38% (169/447) vs 32% (147/466), p=0.047).Conclusion:
At two years, bowel toxicity was similar between SBRT and MHRT, while the incidence of urinary toxicity was higher with SBRT, as measured using RTOG, CTCAE and EPIC-26. Five-year toxicity and efficacy outcomes are awaited.