MultlIple TimepoiNt MRI TO Track Organ At Risk (OAR) Changes In Patients Undergoing Radical Radiotherapy for Head and Neck Cancer
In many patients, the anatomy of the area treated with radiotherapy changes significantly during treatment. This is particularly relevant for patients receiving radiotherapy for head and neck cancer. These tumours can shrink rapidly, whilst patients often lose weight, and important organs at risk such as the salivary glands may change as a direct result of radiation damage. Therefore, there are substantial changes in size, shape and position of organs at risk during treatment, which can lead to significant differences between planned and delivered radiation dose, and impact on the risk of long-term toxicity. These changes can be seen and measured on our daily ‘position-check’ CT scans, but these images can be quite noisy meaning that precise measurement is difficult. MRI scans gives better definition soft tissue definition than is possible with CT, and it has been used to describe changes in salivary gland anatomy pre to post radiotherapy. Functional MRI also gives the possibility to assess the biology of changes occurring in soft tissue, and post-treatment MRI biomarkers have shown strong links to late radiotherapy toxicity.
Methods and Objectives
In the MINOT-OAR sub-study, patients with HNC will be invited to undergo a brief MRI scan at the beginning of the treatment course, and at 3 separate timepoints thereafter during their course of radiotherapy. Patients will be scanned just before their first treatment and then during weeks 2, 4 and 6 of treatment. These images will be a powerful tool for the wider VoxTox programme. The nature and time course of changes in both the parotid and submandibular glands will be defined and will help to train tools for automated identification of these structures on MVCT images. This will improve our ability to accurately calculate delivered radiation dose and predict toxicity. Furthermore, MRI biomarkers measured at the end of treatment have been shown to predict toxicity, and we will look at the presence of these biomarkers earlier in the patient’s course of treatment. By combining this data with information about radiotherapy dose we aim to select patients who will benefit from having their radiotherapy plan adapted during treatment, thereby reducing the risk of severe and lasting treatment side effects.