Factors associated with functional ability in patients with esophageal cancer undergoing chemoradiotherapy: a prospective longitudinal study Running head: Patient functional ability in unresectable EC

Purpose During and after treatment, esophageal cancer (EC) patients experience changes in body mass index (BMI), performance status, nutrition status, symptom distress, and physical fitness. This study aims to evaluate temporal changes and their associated factors in BMI, performance status, nutrition status, symptom distress, physical fitness, and functional ability in EC patients during and after treatment. Methods This prospective longitudinal study recruited EC patients from a medical center in Northern Taiwan. The 112 EC patients were assessed before treatment (T0), 1 month after starting treatment (T1), 3 months after starting treatment (end of treatment) (T2), and 6 months after starting treatment (T3). Generalized estimating equation analysis was used to determine the factors associated with changes in functional ability over time. Results Patient nutrition status was lowest before treatment and then increased by 6 months after treatment. Symptom distress slightly decreased from before treatment to 3 months after treatment, rising at 6 months after treatment but not reaching baseline (T0). Functional ability increased from before treatment to 1 month after treatment and then declined at 3 months after starting treatment, increasing at 6 months to below baseline (T0). Patients who had a BMI less than 25 kg/m ² , engaged less in physical activity, and were less physically fit were more likely to have worse functional ability. Conclusion BMI, level of physical activity, and the degree of physical fitness were the important factors associated with functional ability in EC patients. Healthcare professionals should design patient-tailored prehabilitation programs in advance to strengthen physical fitness.