To observe the critical weight loss(weight loss rate>5%) in patients with head and neck cancer (HNC) during radiotherapy and analyze its influencing factors.

Patients with head and neck cancer treated with radiotherapy in a cancer hospital in Beijing from March 2017 to September 2019 were recruited. The day before the beginning of radiotherapy, general information was collected, and Nutritional Risking Screening 2002 (NRS2002) was used as a nutritional screening tool. Malnutrition was assessed by criteria: 1.the score of normal nutritional status in NRS2002 was 3; 2.body mass index<18.5 kg/m² with poorer general condition; 3.Global leadership initiative on malnutrition criteria was used except whole body muscle mass measurement. Dietary intake was recorded by 24-hour dietary recall. The weight of patients before and after radiotherapy was recorded.

435 patients were completely investigated. The average weight of patients was 65.52 kg±12.20 kg before radiotherapy, and 61.01 kg±11.17 kg after radiotherapy. The weight loss was 4.50 kg±3.17 kg(-3.20~20.90 kg), and the weight loss rate was 6.72%±4.34 %(-5.19%~25.49%). 66.0% of patients had critical weight loss. Multifactor logistic regression analysis showed that the influencing factors of critical weight loss were planned radiotherapy dose (OR=1.069, 95% CI=1.014~1.127, P=0.013), concurrent chemoradiotherapy (OR=1.798, 95% CI=1.148~2.816, P=0.010), baseline malnutrition (OR=2.693, 95% CI=1.223~5.933, P=0.014) and nasopharyngeal tumors (OR=2.059, 95% CI=1.158~3.661, P=0.014).

HNC patients experience significant critical weight loss during radiotherapy. Patients with more planned radiotherapy dose, concurrent chemoradiotherapy, nasopharyngeal tumors and without malnutrition at baseline are at high risk of having critical weight loss. It is suggested that clinical medical staff should pay more attention to patients' weight loss during radiotherapy, give corresponding preventive measures, strengthen nutrition education, and increase the intake of energy and protein and provide nutritional support when necessary to improve the critical weight loss.

Head and neck cancer; Radiotherapy; Critical weight loss; Influencing factor