Author: Yong Chen, Christina Henson, Yuchen Qiu, Marti Roper 👨🔬
Affiliation: University of Oklahoma HSC, University of Oklahoma Health Sciences Center, University of Oklahoma, University of Oklahoma Health Science Center 🌍
Purpose: Traditionally, Head and Neck cancer patients have one or two treatment replans through their treatment course, which fails to account for anatomical changes in position, weight loss, or tumor shrinkage. However, Accuray Radixact machine integrated with high quality fan-beam CT imaging, adaptive daily replans are achievable, allowing for the precise alignment of the changing target volume. This study aims to perform a dosimetric comparison for patients without a treatment replan, with one or more replans, and those undergoing daily replans on the Radixact machine.
Methods: A head and neck patient with 25 fractions was considered for the first patient in the study. This patient was treated on the Radixact machine, with an original treatment plan and one treatment replan, yet has 25 CT scans. Using the MIM software program, the max dose, min dose, and mean dose were recorded from the dose-volume histogram in order to calculate the OAR dose. The OAR dose was calculated in two scenarios: 1.) Assuming the original treatment plan was used for all 25 fractions. 2.) A unique treatment plan was generated for five of the 25 CT scans, again summing the OAR doses for the five plans to mimic daily replans.
Results: When comparing the original plan with the five replans, the most substantial difference observed was the OAR dose for the brain stem, which increased ten percent from the first CT to the last CT. Additionally, a trend of increasing dose to the oral cavity was also seen, about 2% percent overall. This study highlights that daily adaptive replans lower total OAR dose for head and neck cancer patients, particularly when considering the brain stem.
Conclusion: This study demonstrates that daily replans will lower OAR and total dose to patients, which will certainly have significant clinical implications.