Integration of Adaptive Proton Therapy in Pediatric Solid Tumors and Hodgkin's Lymphoma

Proton therapy is a type of radiation treatment that can target tumors very precisely while protecting healthy organs. This is especially important for children. However, during the several weeks of treatment, a child's body and tumor can change. These changes may cause the radiation dose to miss part of the tumor or give too much dose to nearby organs. In usual care, proton therapy plans are based on one CT scan taken before treatment starts. New scans are only done if the care team thinks a change has occurred. There is no standard process to regularly check whether the treatment plan is still accurate during therapy. This study tests a structured approach to monitoring and adjusting proton therapy plans during treatment in children with solid tumors or Hodgkin's lymphoma. About 100 pediatric patients receiving proton therapy at St. Jude Children's Research Hospital will take part. All patients will receive their prescribed proton therapy as usual. The study does not change the radiation dose or schedule. Participants will receive additional CT scans, and MRI when needed, during treatment. Imaging will be done weekly or every other week to check whether the original treatment plan still provides good tumor coverage and protects healthy organs. The treatment plan will be updated if: * Tumor coverage drops by more than 5%, or * Radiation dose to normal organs increases by 10% or more. If these changes are not seen, the original plan will continue. The extra imaging uses a low radiation dose. The goal of this study is to learn how often proton therapy plans need to be adjusted to keep treatment accurate and safe. Results may help improve proton therapy care for children in the future.