A treatment planning comparison of proton therapy and intensity-modulated radiotherapy (IMRT) for prostate cancer using the normal tissue complication probability (NTCP).

Authors

null

Benjamin Walker Fischer-Valuck

Washington University in St. Louis, Department of Radiation Oncology, St. Louis, MO

Benjamin Walker Fischer-Valuck , Lindsey Olsen , Thomas Mazur , Michael Altman , Beth Bottani , Hiram Alberto Gay , Jeff M. Michalski

Organizations

Washington University in St. Louis, Department of Radiation Oncology, St. Louis, MO, Department of Radiation Oncology, Washington University in St. Louis, St. Louis, MO, Washington University School of Medicine in St. Louis, St. Louis, MO

Research Funding

No funding sources reported

Background: The volume of rectum receiving high-dose (i.e. > or = 60 Gy) is consistently associated with the risk of Grade > or = 2 rectal toxicity or rectal bleeding based on common terminology criteria for adverse events (CTCAE). Our goal was to compare intensity-modulated photon radiotherapy (IMRT) with proton radiotherapy in regard to the rectal dose using the normal tissue complication probability (NTCP). Methods: Between July 2014 and September 2015 the first 10 consecutive low or intermediate risk prostate cancer patients were treated with proton therapy at our institution. All 10 patients were planned with three-dimensional conformal proton therapy (3D-CPT) using two parallel opposed fields as well as comparison IMRT plans. A rectal balloon filled with water was used in all patients treated. Prescribed dose to the prostate was 79.2 Gy or cobalt Gy equivalent (CBE) for protons. Dose-volume histograms were compared. The Lyman-Kutcher-Burman model (n = 0.09, m = 0.13, and TD50 = 76.9 Gy) was used to generate NTCP estimates for both IMRT and proton plans. Results: At least 95% of the planning target volume received the prescription dose for both proton and IMRT plans. Dose constraints placed on the rectum included volume receiving 65 Gy (V65) less than 17% and V40 less than 35%. The mean dose to the rectum was 24.5 Gy (range, 19.5-30.1 Gy) and 31.7 Gy (range, 23.7-39.4 Gy) for the proton and IMRT plans, respectively. The V65 constraint was unachievable in 3 of the proton plans and 3 of the IMRT plans. The mean V70 andV75 for proton plans was 8.4% and 5.4% compared to 7.5% and 4.8% for the IMRT plans. The mean NTCP for proton treatment plans was 7.72% (range, 2.7-11.7%) and 7.92% (range, 1.7-15.3%) for IMRT (P = 0.45). After median follow-up of 6 months, no grade 2 or higher toxicity has been reported. Conclusions: Utilizing NTCP estimations, proton therapy and IMRT have similar predicted rates of rectal toxicity. Currently, a Phase III randomized clinical trial is underway comparing proton therapy and IMRT with regards to rectal toxicity and quality of life.

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Abstract Details

Meeting

2016 Genitourinary Cancers Symposium

Session Type

Poster Session

Session Title

Poster Session B: Prostate Cancer; Urothelial Carcinoma; Penile, Urethral, and Testicular Cancers

Track

Urothelial Carcinoma,Prostate Cancer,Penile, Urethral, and Testicular Cancers

Sub Track

Prostate Cancer - Localized Disease

Citation

J Clin Oncol 34, 2016 (suppl 2S; abstr 153)

DOI

10.1200/jco.2016.34.2_suppl.153

Abstract #

153

Poster Bd #

C12

Abstract Disclosures

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