Dosimetric Impact of Inter-Fraction Anatomical Changes in Carbon Ion Boost Treatment for High-Risk Prostate Cancer (AIRC IG 14300)

Abstract

Rectum and bladder volumes play an important role in the dose distribution reproducibility in prostate cancer adenocarcinoma (PCa) radiotherapy, especially for particle therapy, where density variation can strongly affect the dose distribution. We investigated the reliability and reproducibility of our image-guided radiotherapy (IGRT) and treatment planning protocol for carbon ion radiotherapy (CIRT) within the phase II mixed beam study (AIRC IG 14300) for the treatment of high-risk PCa. In order to calculate the daily dose distribution, a set of synthetic computed tomography (sCT) images was generated from the cone beam computed tomography (CBCT) images acquired in each treatment session. Planning target volume (PTV) together with rectum and bladder volume variation was evaluated with sCT dose-volume histogram (DVH) metric deviations from the planning values. The correlations between the bladder and rectum volumes, and the corresponding DVH metrics, were also assessed. No significant difference in the bladder, rectum, and PTV median volumes between the planning computed tomography (pCT) and the sCT was found. In addition, no significant difference was assessed when comparing the average DVHs and median DVH metrics between pCT and sCT. Dose deviations determined by bladder and rectum filling variations demonstrated that dose distributions were reproducible in terms of both target coverage and organs at risk (OARs) sparing.

Optimizing 3DCT image registration for interfractional changes in carbon-ion prostate radiotherapy

“…Other studies use PTV for interfractional dose assessment 23 , 25 , 35 ; however, we evaluated target coverage using CTV. The International Commission on Radiation Units & Measurements (ICRU) Report 78 defines internal margins to compensate for internal uncertainties such as physiologic movement and variations in size, shape, and position of the CTV and uncertainties in factors external to the patient such as setup error 36 .…”

“…Russo et al . evaluated interfractional dose distribution using serial cone-beam CT with bony structure registration, and concluded that dose variations due to rectal and bladder volume variations could be improved by image guidance 35 . However, interfractional change resulted in degraded target coverage for some fractions.…”

Stereotactic body radiation therapy (SBRT) for prostate cancer: Improving treatment delivery efficiency and accuracy

“…Computed tomography (CT) scans were acquired using a Philips Brilliance Big Bore CT scanner according to our clinical protocol and registered with multiparametric magnetic resonance imaging (mpMRI). Prior to treatment simulation and delivery, patients were asked to follow a preparation protocol similarly to Russo et al [17] to limit prostate mobility and achieve anatomical reproducibility (full bladder, empty rectum). The clinical target volume (CTV) was defined as the whole prostate and the proximal 5–10 mm of seminal vesicles.…”

The Role of Carbon Ion Therapy in the Changing Oncology Landscape—A Narrative Review of the Literature and the Decade of Carbon Ion Experience at the Italian National Center for Oncological Hadrontherapy

“…At CNAO, patients with high-risk prostate cancer are currently treated with 66.4 GyRBE for CIRT delivered in 16 sessions, as derived from the NIRS schedule. We participated in a phase II feasibility study (NCT02672449) of a mixed-beam approach including an anticipated CIRT boost (16.6 GyRBE in 4 fractions), followed by pelvic photon IMRT (up to 50 Gy) for high-risk prostate cancer [53,54], thereby showing promising preliminary feasibility and safety findings. Indeed, no gastrointestinal or genitourinary toxicities were recorded after 1 and 3 months from the whole course of RT.…”