Determining The Optimal Time To Apply Adaptive Radiotherapy Plan For Head And Neck Cancer Patients

Background: Head and neck cancer (HNC) patients may have considerable anatomical alterations with IMRT and VMAT. Maintaining dosage precision and minimizing tissue damage using adaptive radiotherapy (ART) improves patients' quality of life. However, the optimal time to initiate ART in HNC patients remains undetermined. Objective: This research aimed to identify the optimal time to start ART in HNC patients using a novel method to evaluate anatomical modifications. Materials and Methods: The research included 48 people with HNC who had undergone dynamic IMRT. The size of the patient's PTV was used to divide them into different groups. Both the ER of the original PTV and the ER of the revised PTV were determined. ER differences (dER) were correlated with volume decrease percentage (%dV). Pre-treatment CT images were taken, and then again at fractions 7, 14, and 21 throughout therapy. Results: The PTV volume distributions were verified to be expected. Small, medium, and high ER volumes showed statistically significant variations between the first and second phases (p<0.001). Fraction 14 was the optimum time to administer ART in cases with a PTV of less than <100cc, whereas fractions 7 and 21 were best for cases with a PTV of 100cc to 500cc. Conclusions: The optimal time to begin PTV-based adaptive radiotherapy in HNC patients has been determined. The ER technique improves the clarity of presenting the gap between the reference isodose volume and the PTV, which is valuable information for ART.