A.M.L. Olteanu

SU‐E‐J‐49: Evaluation of Deformable Image Co‐Registration in Adaptive Dose Painting by Numbers for Head and Neck Cancer

Purpose: To evaluate the accuracy of automated contour deformation for head‐and‐neck cancer in adaptive treatment. Methods: Data from 13 head‐and‐neck patients in a phase I trial for adaptive treatment were used. Adaptation was based on [18F]FDG‐PET‐guided dose painting by numbers (DPBN) plans. Each patient had two DPBN plans based on: (i) a pretreatment PET/CT scan and (ii) a during‐treatment PET/CT scan acquired after 8 fractions. Contours manually drawn on the pretreatment CT scan were deformed using commercial deformable image registrationsoftware onto the during‐treatment CT scan. Deformed contours of regions of interest (ROIdef) were visually inspected by an experienced radiation oncologist and, if necessary, adjusted (ROIdef_ad) and both sets of contours were compared to manually redrawn ROIs (ROIm) using Jaccard (JI) and overlap indices (OI). ROI indices and volumes were compared for all contour sets used a paired t‐test and one‐way ANOVA pairwise comparison, respectively. Results: Almost all deformed ROIs in all patients required adjustment after visual inspection. The largest adjustments were made in GTVs when substantial tumor regression occured, e.g., ROIdef=9.2 cm3 vs. ROIdef_ad=2.2 cm3 vs. ROIm=2.1 cm3. The swallowing structures were the most frequently adjusted ROIs. The mandible was the most acurately propagated ROI requiring little or no adaptation: JI=0.7 and OI=0.8. The upper esophageal sphincter was the worst propagated ROI: JI=0.3 and OI=0.3 for the ROIdef, JI=0.5 and OI=0.6 for the ROIdef_ad. Despite the variation in indices, there was no statistically significant difference between ROIdef, ROIdef_ad and ROIm volumes. Generating ROIm took 4–6 hours, generating ROIdef took a few minutes and generating ROIdef_ad took less than 2 hours. Conclusions: Deformable image co‐registration followed by visual inspection does require adjustment of most deformed ROIs. Nevertheless, fast automatic ROI propagation followed by user‐driven adjustments appears to be more efficient than labor intensive de‐novo re‐contouring.

PO-0638: Adaptive dose painting by numbers for head and neck cancer: interim analysis of a randomised trial

ESTRO 35 2016 ______________________________________________________________________________________________________ studies, topical clonidine shown activity in reducing NF-κB activation and incidence of severe OM (SOM). In a randomized double blind, placebo-controlled study, a novel mucoadhesive buccal tablet (MBT) containing clonidine reduced the incidence of SOM in HNC patients being treated with CRT. We now report overall survival (OS), tolerability and systemic exposure of clonidine of study subjects.

PO-0886: Three phase adaptive 18F-FDG-PET-voxel intensity-based VMAT versus 6-beam IMRT for head-and-neck cancer

Purpose/Objective: In this study we investigated the implementation of a new class-solution of volumetric modulated arc therapy (VMAT) for a three-phase adaptive FFDG-PET-voxel-based dose-painting-by-numbers (DPBN) doseescalation treatment. VMAT dose distributions were compared to the ones made using a standard 6-beam static intensity modulated radiotherapy (sIMRT) technique. Materials and Methods: 10 non-metastatic head-and neck cancer patients, enrolled in the adaptive arm of a phase II DPBN trial were planned both with sIMRT and VMAT. Separate treatment plans based on two pre and per-treatment (after the 8 fraction) F-FDG-PET/CTs and one per-treatment CT (after the 18 fraction) were made according to the trial protocol (Table 1). Dose distributions were summed on the pretreatment CT. Plans were evaluated in terms of dose levels, dose painting quality factors (QFs), treatment time and verified with Delta (Scandidos, Uppsala, Sweden) measurements. Table 1. Prescribed fraction dose for the three phase adaptive treatment protocol. The treatment plans for the first 2 phases were based on the F-FDG-PET/CT information, while for the third phase only CT data was used. Abbreviations: GTV = gross tumor volume; PTVHR = high-risk planning target volume (3 mm expansion of the high-risk clinical target volume CTVHR); CTVHR = a three-dimensional GTV expansion of 1 cm adjusted to air cavities and uninvolved bones.

SP-0033: Adaptive dose painting early experiences

Despite attempts of treatment intensification, improvement of radio(chemo)therapy outcome in head-and-neck cancer remains marginal. Non-selective dose escalation in large planning volumes has not increased the rates of disease control and survival but severe debilitating treatment-induced toxicity. The use of biological imaging in radiotherapy allows detecting other than anatomical imaging-defined targets and enables tailoring dose prescription to tumor biology, .i.e. dose painting [1]. Dose painting can be employed in treatment intensification by non-uniformly escalating dose at no or minimal theoretical increase in the rates of treatment-induced toxicity relative to conventional or 3D-conformal radiotherapy [2]. Because of changes in tumor and non-tumor anatomy and biology throughout treatment, radiotherapy should not be based solely on pretreatment anatomical and biological imaging but adapted to occurring changes detected by pertreatment imaging. Combination of treatment adaptation with dose painting presents a new paradigm of treatment individualization with the promise of substantial improvement of treatment outcome. In Ghent University Hospital we tested dose painting in 41 head-and-neck cancer patients during 2003-2005 demonstrating feasibility of homogenous dose escalation up to 77.5 Gy in 18[F]FDG-PET-based subvolumes within the gross tumor volumes [3]. We introduced adaptive strategy in dose painting (18[F]FDG voxel intensity-based IMRT) in 2007 firstly in a clinical phase I trial with one per-treatment adaptation (21 patients) [4,5] and then in a clinical phase I trial with two per-treatment adaptations (10 patients) [6]. Significant non-homogenous dose escalation in the former trial (Normalized isoeffective dose equivalent to dose delivered in 2.0-Gy fractions [NID2Gy] of 91 Gy at the first level of dose escalation and 102 Gy at the second level of dose escalation) and adaptive procedures using deformable image co-registration in the latter trial were technically feasible and clinically tolerable. Update of clinical results of the trials will be presented at the meeting. The encouraging results of the only clinical trial on combined biologicalimage guided and adaptive IMRT [4,5] supported initiation of a clinical phase II randomized trial currently running in Ghent University Hospital [NCT01341535]. The trial compares adaptive dose painting against standard IMRT with increased loco-regional control and diminished treatment-induced toxicity as primary and secondary objectives, respectively.