Phase Angle as an Early Functional Biomarker of Cancer-Related Fatigue in Pediatric Oncology: A Prospective Longitudinal Study.

BACKGROUND

Pediatric cancer remains a leading cause of morbidity and mortality worldwide, particularly in low-and middle-income countries. Cancer treatment may impair nutritional status, alter body composition, and exacerbate cancer-related fatigue (CRF). Phase angle (PhA), a bioelectrical impedance-derived marker of cellular integrity, has emerged as a potential noninvasive indicator associated with functional status, yet its role in pediatric oncology remains underexplored.

OBJECTIVE

To investigate longitudinal changes in nutritional status and CRF and to examine the association between PhA and CRF in children/adolescents with cancer during the first 3 months of treatment.

METHODS

Prospective longitudinal study included children/adolescents (0-18 years) newly diagnosed with cancer or central nervous system (CNS) tumors. Participants were assessed at diagnosis-[T0], 1 month-[T1], and 3 months-[T2] after treatment initiation. Data collected included clinical/sociodemographic characteristics, nutritional status (anthropometry/STRONGkids), body composition, and CRF (PedsQLMFS). Repeated measures analyses and linear mixed models were performed, with α = 5%.

RESULTS

A total of 23 patients (mean age 5.7 years old; 65.2% female) were included. Over time, significant reductions were observed in body mass index (p = 0.044), PhA (p = 0.013), and lean mass (p = 0.037). Self-reported fatigue worsened, particularly in the general fatigue domain (p = 0.043). Correlation analyses demonstrated significant associations between fatigue and body composition indicators, particularly calf circumference (r = 0.809-0.861), body fat mass (r = 0.756-0.844), and PhA (r = 0.521-0.752) in self-reports. In linear mixed-effects models, PhA was independently associated with total fatigue over time (β = 19.97; p = 0.011).

CONCLUSIONS

Children and adolescents undergoing cancer treatment experience early deterioration in nutritional status and body composition, accompanied by worsening CRF. Fatigue was consistently associated with PhA and lean mass-related indicators, suggesting that body composition and cellular integrity may be associated with fatigue severity during treatment. PhA emerged as a particularly promising noninvasive marker, independently associated with fatigue over time. These findings support the incorporation of PhA and comprehensive nutritional assessment beyond conventional weight- and height-based measures to improve the early identification of patients at risk.