Adaptive 3D-CRT with CCRT for head and neck cancer: resource limited single center experience in Bangladesh

Anatomical changes during Head and Neck Cancer (HNC) radiotherapy can compromise target volume dose coverage and Organs at Risk (OARs) sparing. This study evaluated the volumetric, dosimetric, clinical, and cost-effectiveness impacts of Adaptive Radiotherapy (ART) in HNC patients treated with Three-Dimensional Conformal Radiotherapy (3D-CRT) and Con-Current Chemo-Radiotherapy (CCRT) in resource-limited settings. Fifteen patients with advanced HNC were treated using 3D-CRT with CCRT to a total dose of 70 Gray (Gy) in 35 fractions. A repeat Computed Tomography (re-CT) simulation was performed at 44 Gy due to anatomical changes such as weight loss and tumor shrinkage during the treatment. Adaptive plans were generated using the re-CT images. Pre- and re-CT simulation images were fused, and Planning Target Volumes (PTVs) from the initial and adaptive plans were compared to evaluate the volumetric changes. Adaptive plans were then compared with the initial plans using Dose-Volume Histograms (DVHs), and dosimetric variations in Gross Tumor Volume (GTV), Clinical Target Volume (CTV), and PTV were evaluated. Target coverage deterioration observed with 3D-CRT was mitigated by ART, resulting in improved coverage for both high- and low-dose target volumes compared with the accumulated planned dose. The mean body weight ratio was 0.88 (12% weight loss), and the mean PTV volume ratio up to 44 Gy was 0.76 (24% reduction). Adaptive plans reduced the relative mean dose to the spinal cord 3.2%, brainstem 1.4%, ipsilateral parotid 4.10%, contralateral parotid 2.75%, esophagus 7.40%, mandible 3.60%, and oral cavity 5.60%, while dose coverage of GTV, CTV, and PTV improved by 3.50%, 3.06%, and 2.67%, respectively. ART combined with 3D-CRT and CCRT enhances target coverage while reducing doses to OARs. Re-CT-based adaptive planning at approximately 44 Gy appears to be a feasible and cost-effective strategy for maintaining dosimetric accuracy and adapting to volumetric changes in resource-limited settings.