Sparing the penile bulb in the radical irradiation of clinically localised prostate carcinoma: A comparison between MRI and CT prostatic apex definition in 3DCRT, Linac-IMRT and Helical Tomotherapy

Lucia Perna, Claudio Fiorino, Cesare Cozzarini, Sara Broggi, Giovanni Mauro Cattaneo, Francesco De Cobelli, Paola Mangili, Nadia Di Muzio, Riccardo Calandrino

Research output: Contribution to journalArticlepeer-review

Abstract

Background and purpose: To assess the impact of using MRI and Helical Tomotherapy (HT) compared to 3DCRT and dynamic IMRT on the dose to the penile bulb (PB). Materials and methods: Eight patients diagnosed with prostate cancer entered a treatment protocol including CT and MRI simulation. The prostate apex was defined on both MRI and CT. Treatment plans (HT, Linac-IMRT, 3DCRT and conventional technique), were elaborated on both MRI and CT images. A dose of 71.4 Gy (2.55 Gy/fraction) was prescribed; it was requested that PTVs be covered by 95% isodose line. The mean dose and V50 of PB were evaluated. Results: PTV-MRI plans reduced PB mean dose and V50 compared to PTV-CT plans. This improvement, deriving also from the treatment modality, was 89% for 3DCRT, 99% for Linac-IMRT and 97% for HT (p <0.01), considering V50. Conventional plans resulted in a significantly higher mean PB dose/V50 compared to 3DCRT-PTV-CT (+27%/+38%), Linac-IMRT-PTV-CT (+42%/+57%) and HT-PTV-CT (+32%/+48%) (p <0.01). The comparison between conventional and PTV-MRI techniques showed a still larger increase: +73%/+93% 3DCRT; +86%/+99% Linac-IMRT; +56%/+99% HT (p <0.01). The PB mean dose reduction with Linac-IMRT compared to 3DCRT was 24% (p = 0.034) and 40% (p = 0.027) for PTV-CT and PTV-MRI, respectively. This gain remained significant even when comparing Linac-IMRT to HT: 21% (p = 0.07) PTV-CT and 68% (p = 0.00002) PTV-MRI. HT was superior to 3DCRT with respect to PTV-CT (average gain 4%, p = 0.044), whereas it resulted to be detrimental considering PTV-MRI (26 Gy vs 16.5 Gy), possibly due to the helical delivery of HT; however, in a patient where the distance bulb-PTV

Original languageEnglish
Pages (from-to)57-63
Number of pages7
JournalRadiotherapy and Oncology
Volume93
Issue number1
DOIs
Publication statusPublished - Oct 2009

Keywords

  • 3DCRT
  • Erectile dysfunction
  • IMRT
  • MRI treatment planning
  • Prostate radiotherapy
  • Tomotherapy

ASJC Scopus subject areas

  • Hematology
  • Oncology
  • Radiology Nuclear Medicine and imaging

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