FDG PET-CT for Lymphoma Radiotherapy Planning Version 1.3

Chemotherapy followed by radiotherapy is used to treat early stage lymphomas with excellent cure rates. However, a significant proportion of these patients develop cancers and heart diseases years later as a result of the radiotherapy. Therefore, there is a move to reduce radiation exposure without compromising cure rates. Radiotherapy is planned using a CT scan taken following chemotherapy when many of the original sites of the lymphoma are no longer visible using a CT scan taken following chemotherapy when many of the original sites of the lymphoma are no longer visible. In order to safely minimise the volume treated with radiotherapy it is necessary to accurately reconstruct the extent of the lymphoma prior to chemotherapy on this 'planning' CT scan. A PETCT prior to chemotherapy is the best way of demonstrating the original extent of the lymphoma, but is taken in a different position to the radiotherapy treatment position. This aim of this study is to explore whether a PETCT scan taken prior to chemotherapy in the radiotherapy treatment position, in conjunction with advanced software to combine this scan with the subsequent radiotherapy planning CT, can be used to more accurately identify the lymphoma target. The study aims to recruit up to 20 patients with early stage Hodgkin lymphoma or high grade nonHodgkin lymphoma. A routine staging PETCT will be followed at the same session by a PETCT in the radiotherapy treatment position appropriate radiotherapy immobilisation devices. Participation in the study will not affect treatment decisions or the radiotherapy planning process. The PETCT in the radiotherapy planning position will be made available to the treating clinicians. The process of planning radiotherapy will not be systematically altered by the study. The study is aimed at determining how to improve the radiotherapy planning process in the future, in the hope of a reducing in the long term side effects of treatment whilst retaining high cure rates.