A case study of reproducibility and dose sparing of the testis during radiotherapy

Testes exist as a highly radiosensitive organ at risk (OAR) in which absorbed dose can be significantly impacted by small positional variations. In this case study, challenges arose during radiation therapy treatment regarding immobilization and positional reproducibility of the patient's left testis and penis related to the body's homeostatic response to variable room temperatures. Researchers aimed to describe how the OAR constraints were maintained when room temperatures impacted scrotal positioning by comparing daily localization scans using computed tomography on rails (CToR) to evaluate the dose distribution. In this single pediatric case study, a patient diagnosed with paratesticular sarcoma received intensity modulated proton therapy (IMPT) treatment to the right inguinal region. Immobilization and positional reproducibility inconsistencies of the penis and left testis led to multiple replans. A retrospective statistical analysis of the OAR metrics in 3 radiation treatment plans determined specific patient warming instructions yielded a consistent reproducible outcome along with increased dosimetric accuracy. Understanding the human physiological response to ambient factors, such as room temperature, led to stable reproducibility of the OAR using thermal management. Iterative planning and collaboration between radiation therapy professionals were also key elements that paved the way to maintain treatment planning constraints.