gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

A Dosimetric Comparison of IMPT versus IMRT for Early-Stage Prostate Cancer

Meeting Abstract

  • M. N. Corradetti - Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
  • R. Scheuermann - Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
  • D. Curtiland - Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
  • Z. A. Tochner - Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
  • S. Both - Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
  • N. Vapiwala - Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog046

DOI: 10.3205/09ptcog046, URN: urn:nbn:de:0183-09ptcog0468

Published: September 24, 2009

© 2009 Corradetti et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


Outline

Text

Purpose: Intensity modulated radiotherapy (IMRT) is a mainstay of treatment for prostate adenocarcinoma, along with interstitial brachytherapy, surgical resection, and watchful waiting. The aim of this dosimetric study is to compare intensity-modulated photon radiotherapy (IMRT) with intensity-modulated proton therapy (IMPT) for early-stage prostate cancer patients.

Methods and materials: Eight patients with early-stage prostate cancer were simulated with CT and/or MRI with endorectal balloon and were treated with 7-field IMRT at the Hospital of the University of Pennsylvania. For comparison purposes, 2-field IMPT plans using opposed lateral beams were generated. The prescription dose to the clinical target volume (CTV), which included the entire prostate and proximal seminal vesicles, was 79.2 Gy for IMRT plans and 79.2 Gy(RBE) for IMPT plans. Our institutional constraints for the bladder, rectum, and femoral heads (the primary organs at risk, or OAR) were: bladder V45 < 50% and V65 < 20%; rectum V40 < 50% and V60 < 20%; femoral heads V37 < 50% and V50 <10%. Dose volume histograms (DVH) of the CTV and of the primary OARs were compared. Statistical analysis of DVH indicators was performed via Wilcoxon signed rank test.

Results: Both IMRT and IMPT plans were able to deliver, at minimum, 98% of the prescription dose to the CTV. The mean percentage of the bladder receiving less than 45 Gy for IMRT plans (V45Gy) was 25.6% and the mean percentage of the bladder receiving less than 45 Gy for IMPT plans (V45GyRBE) was 15.2% (p<0.01). The bladder V65Gy was 13.4%, and the V65GyRBE was 10.3% (p=0.02). The rectum V40Gy was 42.3% and the V40GyRBE was 24.5% (p<0.01). The rectum V60Gy was 19.0%, and the V60GyRBE was 16.8%, with no statistical significance (p=0.2). There was also no statistically significant difference for the mean percentage of the femoral heads receiving less than 37, 45, or 50 Gy/Gy(RBE) between IMRT and IMPT plans.

Conclusions: Prostate IMPT plans achieved better sparing of the bladder and rectum than IMRT plans for all analyzed DVH indicators except for the rectum V65 (p=0.2). On average, IMPT plans reduced V45 for the bladder by 40.6%, V60 for the bladder by 23.1%, and V40 for the rectum by 11.6%. There was no statistically significant difference between IMRT and IMPT plans for the femoral heads at V37, V45, and V50. Further study will be required to determine whether the dosimetric benefits reported here can be translated into meaningful clinical gains.