Methodology for adaptive and robust FDG-PET escalated dose painting by numbers in head and neck tumors

Abstract

Objective. To develop a methodology for using FDG PET/CT in adaptive dose painting by numbers (DPBN) in head and neck squamous cell carcinoma (HNSCC) patients. Issues related to noise in PET and treatment robustness against geometric errors are addressed. Methods. Five patients with locally advanced HNSCC scheduled for chemo-radiotherapy were imaged with FDG-PET/ CT at baseline and 2-3 times during radiotherapy (RT). The GTV PET was segmented with a gradient-based method. A double median filter reduces the impact of noise in the PET uptake-to-dose conversion. Filtered FDG uptake values were linearly converted into a voxel-by-voxel prescription from 70 (median uptake) to 86 Gy (highest uptake). A PTV PET was obtained by applying a dilation of 2.5 mm to the entire prescription. Seven iso-uptake thresholds led to seven sub-levels compatible with the Tomotherapy HiArt ® Treatment Planning System. Planning aimed to deliver a median dose of 56 Gy and 70 Gy in 35 fractions on the elective and therapeutic PTVs, respectively. Plan quality was assessed with quality volume histogram (QVH). At each time point, plans were generated with a total of 3-4 plans for each patient. Deformable image registration was used for automatic contour propagation and dose summation of the 3 or 4 treatment plans (MIMvista ®). results. GTV PET segmentations were performed successfully until week 2 of RT but failed in two patients at week 3. QVH analysis showed high conformity for all plans (mean V Q  0.95 93%; mean V Q  1.05 3.9%; mean QF 2.2%). Good OAR sparing was achieved while keeping high plan quality. conclusion. Our results show that adaptive FDG-PET-based escalated dose painting in patients with locally advanced HNSCC is feasible while respecting strict dose constraints to organs at risk. Clinical studies must be conducted to evaluate toxicities and tumor response of such a strategy.

PET/CT-guided dose-painting versus CT-based intensity modulated radiation therapy in locoregional advanced nasopharyngeal carcinoma

“…PET). Dose painting enables mapping of dose prescription to non-uniform distribution of metabolic, biochemical, and molecular abnormalities within the tumor [18–20]. FDG-PET/CT is increasingly used in dose painting for NPC.…”

“…Furthermore, FDG-PET directed dose distribution could lead to better sparing of organs at risk, such as parotid glands [22, 23]. Various PET-based threshold methods have been proposed for target volume delineation, including SUV2.5, SUV50%max, and signal/background ratio (SBR) [9, 22, 24, 25]. In this study, SUV50%max target was selected as the clinical standard for dose escalation.…”

Task Group 174 Report: Utilization of [18F]Fluorodeoxyglucose Positron Emission Tomography ([18F]FDG‐PET) in Radiation Therapy

“…In RT, PET image registration is used for the following purposes among others: (a) better tumor target definition; (b) propagation of contours from one image set to another; (c) adaptive therapy planning/dose painting to selectively increase dose to more PET‐avid target regions; and (d) incorporation of respiratory‐gated PET information in treatment planning . The reader is referred to AAPM Task Group 132 (TG‐132: Use of Image Registration and Fusion Algorithms and Techniques in Radiotherapy), which deals with the topic of image registration in RT.…”

“…(c) adaptive therapy planning/dose painting to selectively increase dose to more PET-avid target regions [94][95][96] ; and (d) incorporation of respiratory-gated PET information in treatment planning. [97][98][99] The reader is referred to AAPM Task Group 132 (TG-132: Use of Image Registration and Fusion Algorithms and Techniques in Radiotherapy), 100 which deals with the topic of image registration in RT.…”

18F-Fdg-PET-guided Planning and Re-Planning (Adaptive) Radiotherapy in Head and Neck Cancer: Current State of Art

“…For Differding et al (66) a decrease of target volumes can be shown in the first radiation treatment week. However, replanning is considered optimal after two treatment weeks but no later due to increasing edema and inflammation and the consequent difficult to distinguish boundaries.…”