Adaptive Radiotherapy for Head Neck Cancer

Abstract

Changes in patient anatomy may occur either from a tumour volume, position or function of a specific organ at risk, or target volume, weight loss or a reduction in postoperative oedema, and may vary between patients. Adaptive radiotherapy aims to correct morphological variations by realizing one or more plans during the treatment course. Imaging is used to detect these variations, thereby deciding on a potential replanning. At present, adaptive radiotherapy for head neck cancer (HNC) mainly deals with treatment response, such as weight loss or tumor shrinkage. Therefore a properly timed repeat CT scan during treatment is a suitable basis for plan adaptation to account for treatment response.

Evaluation of Adaptive Radiation Therapy in Treatment of Locally Advanced Head and Neck cancers

“…8 According to Liu et al9, tumor shrinkage can be detected as early as the first two weeks, with median revealed shrinkage rates varying from 3 to 16%, 9 Surcus et al 5 found that tumor size was reduced by the end of the fourth week, with median revealed shrinkage rates ranging from7 to 48%, 5 while Loo et al 10 discovered that the tumor size had shrunk by the end of the 7th week, with median disclosed shrinkage rates varying from 6 to 66%. 10 In our study we found that median primary tumor volume changed from (48.3) cm 3 to (31.26) cm 3 with percentage reduction about (35.2%) at the end of 4th week.…”

“…The whole study group received IMRT radiation therapy with concurrent weekly cisplatin 40mg/m2, target volume coverage of original and boost plan on primary CT (P1), also doses to organs at risk (ipsilateral parotid, contralateral parotid, spinal cord as well as brain stem) are displayed in table (2) The modified IMRT plan increased GTV and PTV2 median coverage by 0.25% and 0.1.27%, respectively; ipsilateral and contralateral parotid volumes were reduced by 13.26% and 17.68%, respectively. Table (3) The median dose decrease to the ipsilateral parotid, contralateral parotid, spinal cord, and brain stem was 3.86%, 5.32%, 3.5%, and 5.28%, respectively, with adaptive replaning. The median coverage for GTV and PTV2 was improved by 0.25% and 0.1.27%, respectively, with the adapted IMRT plan.…”

“…1 Because of the high number of organs at risk in the small neck and head area, as well as the complexities of lymphatic drainage, as well as the high sensitivity of organs at risk to radiotherapy, which results in a high incidence of acute toxicity, intensity-modulated radiation therapy (IMRT) has become the primary strategy for such patients due to its ability to decrease dosages to organs at risk and cover different irregular targets with different dose gradients. 2 During the radiotherapy course that likely extend to 6-7 weeks the tumor as well as some organs at risk like parotid glands change in size and location, these changes not taken in account during the traditional radiotherapy course although this may lead to a lack of target coverage and/or higher dosage for the organs at risk, because of this problem the idea of adaptive radiotherapy (ART) come to practice 3 Many trials have tracked adjustments in target and risk organs throughout radiotherapy treatment courses throughout different schedules of CT, ranging between daily to weekly imaging and found significant geometrical changes that mandate adoptive replanting during the radiotherapy course for at least one time. References required 4 If no adaptive replanning done routinely likely the coverage of the targeted will not be adequate along the treatment course, in addition to that organs at risk may receive radiation dose higher than what is seen in the primary plan and even exceed the predefined tolerance.…”

Quality Assurance Assessment of Intra-Acquisition Diffusion-Weighted and T2-Weighted Magnetic Resonance Imaging Registration and Contour Propagation for Head and Neck Cancer Radiotherapy

“…Most implementations of DIR involve a transformation that establishes a geometric correspondence between fixed and moving images, an objective function, and an optimization approach to maximize the similarity between images [12][13][14]. Importantly, even minor differences in patient anatomy can result in devastating dose administration in HNC [4,15], highlighting the need for consistent image co-registration when propagating segmentations of target volumes and OARs for radiotherapy treatment planning. Therefore, determining the impact of post-acquisition registration techniques (i.e., DIR) on multisequence MRI acquisitions is crucial for MR-guided treatment of HNC.…”

“…Conventionally, RT has relied on radiographic images to enable pre-treatment segmentation of target volumes and nearby organs at risk (OAR) to plan intensity-modulated doses [2,3]. However, throughout RT, the dynamic changes in target volumes and OARs and patientspecific changes (e.g., weight loss) can lead to unintended doses of radiation to OARs and subsequent debilitating side effects [4]. These potential unintended doses are particularly relevant for HNC because the head and neck region is home to various complex, highly radiosensitive structures and tissue interfaces that can drastically change during RT [4,5].…”