Diagnostic and prognostic utility of phase angle in patients with cancer

Patients with cancer experience dynamic and longitudinal changes in nutritional status and body composition along the disease trajectory. They often want to know about their outlook with regard to treatment outcomes and overall survival. One of the commonly used measures for body composition is bioelectrical impedance analysis (BIA). BIA is an easy-to-use, quick, inexpensive, noninvasive, and reproducible technique that is often incorporated in daily clinical practice. Phase angle (PA), which is derived from BIA, is an indicator of cell membrane health and integrity. Higher PA values reflect better cell function, higher muscle mass, and lower fat mass. PA is also thought to be a proxy of water distribution (ratio between extracellular water [ECW] and intracellular water [ICW]) and body cell mass. In this narrative review, we discuss studies examining the diagnostic and prognostic value of PA regarding nutritional status, body composition and physical function, complications of cancer treatments, overall survival, symptoms, and quality of life (QOL) in patients with cancer. The literature suggests that PA is moderately to strongly correlated with body composition and physical function but only weakly correlated with nutritional status, complications, survival, symptoms, and QOL. Furthermore, the PA cutoff values vary significantly according to study and patient population with the diversity of bioelectrical impedance technology and electrode composition and placement. Thus, PA has yet to be routinely incorporated into clinical practice for patients with cancer. Future research is needed to determine how to translate scientific understanding of PA to clinical practice.