Dose–Volume Comparison of Proton Therapy and Intensity-Modulated Radiotherapy for Prostate Cancer

Vargas, Carlos; Fryer, Amber; Mahajan, Chaitali; Indelicato, Daniel; Horne, David; Chellini, Angela; McKenzie, Craig; Lawlor, Paula; Henderson, Randal; Li, Zuofeng; Lin, Liyong; Olivier, Kenneth; Keole, Sameer

doi:10.1016/j.ijrobp.2007.07.2335

« Previous Next »International Journal of Radiation Oncology * Biology * Physics
Volume 70, Issue 3 , Pages 744-751, 1 March 2008

Dose–Volume Comparison of Proton Therapy and Intensity-Modulated Radiotherapy for Prostate Cancer

Carlos Vargas, M.D.
- University of Florida Proton Therapy Institute, Jacksonville, FL
- Reprint requests to: Carlos Vargas, M.D., Department of Radiation Oncology, University of Florida Proton Therapy Institute, 2015 N. Jefferson St., Jacksonville FL 32206
Amber Fryer, B.S.
- University of Florida Proton Therapy Institute, Jacksonville, FL
Chaitali Mahajan, M.D.
- University of Florida Proton Therapy Institute, Jacksonville, FL
Daniel Indelicato, M.D.
- Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL
David Horne, C.M.D.
- University of Florida Proton Therapy Institute, Jacksonville, FL
Angela Chellini, B.S.
- University of Florida Proton Therapy Institute, Jacksonville, FL
Craig McKenzie, C.M.D.
- University of Florida Proton Therapy Institute, Jacksonville, FL
Paula Lawlor, C.M.D.
- University of Florida Proton Therapy Institute, Jacksonville, FL
Randal Henderson, M.D.
- University of Florida Proton Therapy Institute, Jacksonville, FL
Zuofeng Li, D.Sc.
- University of Florida Proton Therapy Institute, Jacksonville, FL
Liyong Lin, Ph.D.
- University of Florida Proton Therapy Institute, Jacksonville, FL
Kenneth Olivier, M.D.
- Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL
Sameer Keole, M.D.
- University of Florida Proton Therapy Institute, Jacksonville, FL

Received 24 April 2007; received in revised form 2 July 2007; accepted 4 July 2007. published online 27 September 2007.

Purpose

The contrast in dose distribution between proton radiotherapy (RT) and intensity-modulated RT (IMRT) is unclear, particularly in regard to critical structures such as the rectum and bladder.

Methods and Materials

Between August and November 2006, the first 10 consecutive patients treated in our Phase II low-risk prostate proton protocol (University of Florida Proton Therapy Institute protocol 0001) were reviewed. The double-scatter proton beam plans used in treatment were analyzed for various dosimetric endpoints. For all plans, each beam dose distribution, angle, smearing, and aperture margin were optimized. IMRT plans were created for all patients and simultaneously analyzed. The IMRT plans were optimized through multiple volume objectives, beam weighting, and individual leaf movement. The patients were treated to 78 Gray-equivalents (GE) in 2-GE fractions with a biologically equivalent dose of 1.1.

Results

All rectal and rectal wall volumes treated to 10–80 GE (percentage of volume receiving 10–80 GE [V₁₀–V₈₀]) were significantly lower with proton therapy (p < 0.05). The rectal V₅₀ was reduced from 31.3% ± 4.1% with IMRT to 14.6% ± 3.0% with proton therapy for a relative improvement of 53.4% and an absolute benefit of 16.7% (p < 0.001). The mean rectal dose decreased 59% with proton therapy (p < 0.001). For the bladder and bladder wall, proton therapy produced significantly smaller volumes treated to doses of 10–35 GE (p < 0.05) with a nonsignificant advantage demonstrated for the volume receiving ≤60 GE. The bladder V₃₀ was reduced with proton therapy for a relative improvement of 35.3% and an absolute benefit of 15.1% (p = 0.02). The mean bladder dose decreased 35% with proton therapy (p = 0.002).

Conclusion

Compared with IMRT, proton therapy reduced the dose to the dose-limiting normal structures while maintaining excellent planning target volume coverage.

Intensity-modulated radiotherapy, Protons, Dose–volume, Prostate cancer, High dose