The impact of weight loss on setup accuracy for head and neck cancer patients in the era of image guided radiation therapy

Abstract

Patients receiving radiation therapy (RT) for head and neck cancers often experience severe weight loss that can lead to difficulty in daily setup. The primary purpose of this study was to understand the impact ofweight loss on patient’s setup in the era of image guided radiation therapy. Materials and methods One hundred and ninety-three consec- utive patients were treated with radiation for head and neck malignancies.Weight loss was measured during weekly treat- ment visits, and percentage weight loss was calculated by dividing the total weight loss by the pre-treatment weight. Kilovoltage (KV) imaging was performed daily to ensure set- up accuracy with shifts recorded on a daily basis in the anterior-posterior (AP), left-right (LR), and superior-inferior (SI) dimensions. Spearman correlation coefficients,Wilcoxon and Kruskal-Wallis tests were used in statistical analysis. A regression model based upon the beta distribution was used to fit multivariate models for percentage weight change. Results The average percentage weight loss for the cohort was 8 % (SD = 6 %).Weight loss was associated with the largest overall shift and the largest LR shift, but not shifts in other dimensions (ρ =<0.025 and ρ =<0.005). No specific weight change threshold was identified to correlate with these shifts. Disease stage, age, oral cavity subsite, and use of chemother- apy were predictive of weight change. Conclusions In the era of dailyKVimaging for head and neck cancer, minimal shifts are needed despite significant weight loss. When weight loss is present, therapists and physicians should pay most attention to the LR dimension to ensure ac- curate treatment setup. This study suggests despite significant weight loss, daily KV imaging offers a high fidelity and reproducibility.