3311 - Baseline Characteristics of Patients Enrolled on the Prostate Advanced Radiation Technologies Investigating Quality of Life (PARTIQoL) Trial Comparing Proton Therapy vs. IMRT for Low or Intermediate R

A. J. Wisdom¹, B. Y. Yeap², J. M. Michalski³, A. L. Zietman⁴, J. P. Christodouleas⁵, S. C. Kamran⁴, R. R. Parikh⁶, N. Vapiwala⁵, W. F. Hartsell⁷, D. T. Miyamoto⁴, J. Zeng⁸, T. M. Pisansky⁹, M. V. Mishra¹⁰, D. E. Spratt¹¹, N. P. Mendenhall¹², E. M. Soffen¹³, J. E. Bekelman⁵, and J. A. Efstathiou⁴; ¹Massachusetts General Hospital, Harvard Medical School, Boston, MA, ²Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, ³Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, ⁴Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, ⁵Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, ⁶Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, ⁷Proton Collaborative Group, Warrenville, IL, ⁸Department of Radiation Oncology, University of Washington - Fred Hutchinson Cancer Center, Seattle, WA, ⁹Department of Radiation Oncology, Mayo Clinic, Rochester, MN, ¹⁰Maryland Proton Treatment Center, Baltimore, MD, ¹¹University Hospitals Seidman Cancer Center, Case Western Reserve University, Cleveland, OH, ¹²Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL, ¹³Princeton Radiation Oncology, Astera Cancer Care, Jamesburg, NJ

Purpose/Objective(s): Men with localized prostate cancer may receive external radiotherapy with either photon-based intensity-modulated radiotherapy (IMRT) or with proton beam therapy (PBT). The PARTIQoL trial (NCT01617161) is the first multicenter phase 3 randomized trial comparing IMRT to PBT in the treatment of localized prostate cancer. Here, we report the baseline features of patients enrolled on this trial. Materials/

Methods: Patients with low- or intermediate-risk prostate cancer were randomized to either PBT or IMRT after stratification for institution, age, use of rectal spacer, and fractionation schedule (conventional fractionation: 79.2 Gy in 44 fractions vs. moderate hypofractionation: 70.0 Gy in 28 fractions). Participants were followed longitudinally to assess patient-reported outcomes of bowel, urinary, and erectile function for 60 months after completion of radiotherapy. The primary endpoint was to compare bowel health related quality of life using the EPIC score at 24 months after completion of radiotherapy. Secondary objectives include treatment-related differences in urinary and erectile functions and efficacy endpoints. Per protocol, no patients received ADT.

Results: Between 06/2012 and 11/2021, 450 patients were randomized to either PBT (N=226) or to IMRT (N=224); 14 were ineligible or withdrew prior to treatment. The median age of the 436 analyzed patients was 68 years (range 46-89). 80% of patients were white, 13% were African-American, 2% were Hispanic, and 1% were Asian/Pacific Islander. 50% had Gleason score 6 and 50% had Gleason score 7. 81% had clinical stage T1c disease, while 18% had cT2a, and 1% had cT2b disease. The median PSA was 6.3 ng/mL (range 1.1-18.9). 41% of patients had low-risk and 59% of patients had intermediate-risk disease. 97% had ECOG performance status 0 and 3% had score 1. Median BMI was 28.7 and 72% of patients had no or mild comorbidities by ACE27, and 24% had moderate comorbidities. 49% of PBT patients were treated with pencil beam scanning. 50% of patients were treated with conventional fractionation and 50% were treated with moderately hypofractionated radiation. For patients receiving PBT, 47% used a rectal balloon, 45% used a rectal spacer, and 5% used both. For patients receiving IMRT, 46% used a rectal balloon, 42% used a rectal spacer, and 5% used both. 99% of all patients had fiducials. PBT and IMRT arms were evenly balanced for baseline variables.

Conclusion: PARTIQoL successfully accrued the target sample of 450 men with low- or intermediate-risk prostate cancer to a prospective, randomized clinical trial in which participants were assigned IMRT or PBT. We continue to monitor participants for primary and secondary endpoints.