Predictive Models to Determine Clinically Relevant Deviations in Delivered Dose for Head and Neck Cancer

Abstract

Purpose: To improve the understanding of deviations between planned and accumulated dose and establish metrics to predict for clinically significant dosimetric deviations midway through treatment to evaluate the potential need to replan during fractionated radiation therapy (RT). Methods and Materials: 100 head and neck cancer patients were retrospectively evaluated. Contours were mapped from the planning CT to each fraction CBCT via deformable image registration (DIR). The dose was calculated on each CBCT and evaluated based on the mapped contours. The mean dose at each fraction was averaged to approximate the accumulated approximate the accumulated dose for structures with max dose constraints. A threshold dose for structures with mean dose constraints and the daily max dose was summed to deviation value was calculated to predict for patients needing mid-treatment replanning. This predictive model was applied to 52 patients treated at a separate institution. Results: Dose was accumulated on 10 organs over 100 patients. To generate a threshold deviation that predicted the need to replan with 100% sensitivity, the submandibular glands required replanning if the delivered dose was at least 3.5Gy higher than planned by fraction 15. This model predicts the need to replan the submandibular glands with 98.7% specificity. On the independent evaluation cohort, this model predicts the need to replan the submandibular glands with 100% sensitivity and 98.0% specificity. The oral cavity, intermediate CTV, left parotid, and inferior constrictor patients each had one patient exceeding the threshold deviation by the end of

Criteria for Verification and Replanning Based on the Adaptive Radiotherapy Protocol “Best for Adaptive Radiotherapy” in Head and Neck Cancer

“…During a typical course of radiotherapy in patients with HN cancer, the average volume reduction in the PGs is 26% [ 3 , 4 , 6 , 8 , 11 , 13 , 18 , 21 , 24 , 26 , 32 , 40 , 41 ]. We grouped the PG volume changes into five groups according to the percentage change ( Table 6 ).…”

Initial Feasibility and Clinical Implementation of Daily MR-Guided Adaptive Head and Neck Cancer Radiation Therapy on a 1.5T MR-Linac System: Prospective R-IDEAL 2a/2b Systematic Clinical Evaluation of Technical Innovation

“…Because offline adaptive replanning is time and resource intensive, many studies have focused on identifying anatomic and dosimetric guidelines to determine when plan adaptation would be optimally effective. 30,31,33 However, the clinical introduction of the 1.5T MR-linac has made daily ART for HNC a feasible clinical reality.…”

Investigation of Autosegmentation Techniques on T2-Weighted MRI for Off-line Dose Reconstruction in MR-Linac Adapt to Position Workflow for Head and Neck Cancers

“…As such, we have elected to take a computationally simpler approach where we reconstruct the dose based on the static anatomy represented in the daily setup image. Our workflow is more closely aligned with previously reported studies where dose is reconstructed based on on-board setup imaging using cone beam CT [41,42] or CT-on-rails [43], with the key difference from these studies being that a unique ATP treatment plan is delivered each day rather than delivering the same plan at each fraction.…”