Genitourinary Cancer

PD 01 - GU 1 - Poster Discussion - New Data on PET, MRI and Protons for Treating Prostate Cancer

1008 - Preliminary toxicity report comparing pencil beam scanning (PBS) to double scatter/uniform scanning proton beam therapy for localized prostate cancer (PC): Analysis of PCG 001-09

Sunday, October 21
2:10 PM - 2:16 PM
Location: Room 217 A/B

Preliminary toxicity report comparing pencil beam scanning (PBS) to double scatter/uniform scanning proton beam therapy for localized prostate cancer (PC): Analysis of PCG 001-09
M. V. Mishra1, R. Khairnar2, S. M. Bentzen3, G. L. Larson4, H. K. Tsai5, C. C. Sinesi6, C. E. Vargas7, G. E. Laramore8, C. J. Rossi9, L. R. Rosen10, and W. F. Hartsell11; 1University of Maryland School of Medicine, Baltimore, MD, 2University of Maryland School of Pharmacy, Baltimore, MD, 3Greenebaum Comprehensive Cancer Center and Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD, 4ProCure Proton Therapy Center, Oklahoma City, OK, 5ProCure Proton Therapy Center, Somerset, NJ, 6HUPTI, Hampton, VA, 7Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 8University of Washington, Department of Radiation Oncology, Seattle, WA, 9Scripps Proton Therapy Center, San Diego, CA, 10Willis-Knighton Proton Therapy Center, Shreveport, LA, 11Northwestern Medicine Chicago Proton Center, Warrenville, IL

Purpose/Objective(s): Although use of proton beam therapy (PBT) continues to be the focus of debate, PBT for treatment of PC is particularly controversial. Randomized controlled trials comparing PBT to photons are currently underway for multiple disease sites, including PC. As data from such studies emerge, some have questioned their relevance, given that these studies have been, at least partially, conducted using “conventional” PBT techniques (uniform scanning/double scatter [US/DS]) rather than more advanced PBS technology. The dosimetric benefits of PBS are well known, but comparative effectiveness data are limited on outcomes with the 2 treatments. The purpose of this analysis is to compare acute/late toxicity rates of PBS with those of US/DS techniques for men with localized PC enrolled in a prospective multicenter registry study.

Materials/Methods: We evaluated acute and late gastrointestinal (GI) and genitourinary (GU) toxicity rates for men with low-to-intermediate risk PC enrolled in PCG 001-09 (NCT01255748). The analysis was limited to men treated with PBT to the prostate ± seminal vesicles with conventionally fractionated radiation using US/DS or PBS techniques. Toxicities were prospectively scored using the CTCAE v4.0 scoring system. Univariate acute GI/GU toxicities between the 2 techniques were compared using chi-squared tests, and multivariable analyses (MVA) for acute toxicity were evaluated using logistic regression. The rate of late GI/GU toxicity was evaluated using cumulative incidence methods, and MVA of late toxicities was analyzed using Cox proportional hazards models. Propensity score adjustments were applied to MVAs for acute and late toxicity to adjust for confounders.

Results: A total of 1,523 men were treated using US/DS (n=1,217) or PBS (n=306). Median follow-up times were 27.5 mo for US/DS and 16.7 mo for PBS. The incidence of acute grade 2+ GI toxicity in PBS did not significantly differ from that with US/DS (2.94% and 2.22%, respectively; P=0.46). The incidence of acute grade 2+ GU toxicity was significantly higher in the PBS cohort (21.90% vs. 16.27%; P<0.05). In MVA using propensity score adjustment, treatment with PBS was significantly associated with increased risk of GU toxicity (OR=1.45; 95%CI=1.20-1.75), even after adjusting for baseline IPSS score. Late grade 2+ GI (HR=1.08; 095%CI=0.62-1.88) and GU toxicity (HR=1.30; 95%CI=0.95-1.79) did not differ significantly between the groups.

Conclusion: This is the first comparative effectiveness evaluation of modern PBT techniques for men with PC. Although no significant differences were found between the groups in late toxicity, differences in acute GU toxicity warrant evaluation and underscore the need for prospective long-term data on outcomes after both techniques.

Author Disclosure: M.V. Mishra: Employee; Orthofix. Research Grant; ASTRO, Keep Punching. Advisory Board; Patient Centers Outcomes Research Institute (PCORI. Travel Expenses; Patient Centers Outcomes Research Institute (PCORI. R. Khairnar: None. S.M. Bentzen: Travel Expenses; University of Copenhagen. H.K. Tsai: None. C.E. Vargas: Stock; View Ray. Chairman; Proton Collaborative Group. G.E. Laramore: Professor and Chair of Department of Radiation Oncology; University of Washington. C.J. Rossi: None. L.R. Rosen: Partner; Radiation Oncology Services. Honoraria; Iba, lane r rosen. Speaker's Bureau; lane r rosen. Travel Expenses; Iba, lane r rosen. Stock; IBA. Board Member; Caddo bossier cancer foundation league. W.F. Hartsell: Partner; Radiation Oncology Consultants, Ltd. Minority owner of GammaKnife equipment; Elk Grove Radiosurgery Inc. Partnership; Elk Grove Radiosurgery Inc, Illinois Cyberknife. Medical Director; Chicago Proton Center.

Mark Mishra, MD

University of Maryland

Disclosure:
Employment
Orthofix: Employee: Employee; University of Maryland: Assistant Professor: Employee

Compensation
ASTRO: Research Grants; Keep Punching: Research Grants; Patient Centers Outcomes Research Institute (PCORI: Advisory Board, Travel Expenses

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1008 - Preliminary toxicity report comparing pencil beam scanning (PBS) to double scatter/uniform scanning proton beam therapy for localized prostate cancer (PC): Analysis of PCG 001-09



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