An analysis of phase angle and standard phase angle cut-off values and their association with survival in head and neck cancer patients undergoing radiotherapy.

Objective: The objective of this study is to identify the cutoff values for phase angle (PA) and standard phase angle (SPA) parameters, as determined by bioelectrical impedance analysis (BIA), for predicting malnutrition and investigating their association with overall survival in head and neck cancer (HNC) patients undergoing radiotherapy.

Methods: In this study, nutritional assessment and follow-up of HNC patients undergoing radiotherapy (RT) between November 2017 and September 2022 were assessed. Nutritional assessment, body composition (BC), and PA results obtained from BIA (Tanita MC-980) were retrospectively evaluated. Statistical Package for Social Sciences (SPSS) version 25.0 (IBM Corp., Armonk, NY, USA) was used for statistical analysis. The results were evaluated at a confidence interval of 95% and a significance level of p ≤ 0.05.

Results: A total of 53 patients, including 37 (70%) men and 16 (30%) women, with a median age of 60 (23-87 years) were included. The median follow-up time was 51 (range 24-59) months. The mean PA of the patients was calculated as 4.99° (±0.92, 95% CI: 4.74-5.25). The PA of patients with malnutrition (4.66° ± 0.87) was lower than that of well-nourished patients (5.71° ± 0.56) (p < 0.001). As a result of the ROC analysis based on this finding, the ideal PA cut-off point for determining the presence of malnutrition was found to be 5.65, with a sensitivity of 85%, specificity of 79%, accuracy of 83%, and a model discrimination power of excellent level (AUC: 85%, p < 0.001). The median overall survival time of the patients was calculated as 51 months (24-59 months). The mortality rate during the follow-up period was 13%, while the 1-, 3-, and 5-year overall survival rates of the patients were 96.1%, 89.3%, and 86.8%, respectively. Patients with SPA values less than -1.65 had a 5-year overall survival rate of 77.4%, while those with SPA values greater than or equal to -1.65 had a 5-year overall survival rate of 100% (p = 0.030) CONCLUSION: Our study recommends using PA and SPA as standard criteria for detecting malnutrition in HNC patients undergoing RT, with cut-off points of 5.65 and -1.65 respectively, to prevent treatment interruptions and improve outcomes. Further research is needed to validate the SPA cut-off value and its relationship with clinical outcomes, as SPA may be a more effective predictor of malnutrition and overall survival than PA alone.