Quantitative body mass characterization before and after head and neck cancer radiotherapy: A challenge of height-weight formulae using computed tomography measurement.

OBJECTIVES: We undertook a challenge to determine if one or more height-weight formula(e) can be clinically used as a surrogate for direct CT-based imaging assessment of body composition before and after radiotherapy for head and neck cancer (HNC) patients, who are at risk for cancer- and therapy-associated cachexia/sarcopenia.

MATERIALS AND METHODS: This retrospective single-institution study included 215 HNC patients, treated with curative radiotherapy between 2003 and 2013. Height/weight measures were tabulated. Skeletal muscle mass was contoured on pre- and post-treatment CT at the L3 vertebral level. Three common lean body mass (LBM) formulae (Hume, Boer, and James) were calculated, and compared to CT assessment at each time point.

RESULTS: 156 patients (73%) had tumors arising in the oropharynx and 130 (61%) received concurrent chemotherapy. Mean pretreatment body mass index (BMI) was 28.5±4.9kg/m(2) in men and 27.8±8kg/m(2) in women. Mean post-treatment BMI were 26.2±4.4kg/m(2) in men, 26±7.5kg/m(2) in women. Mean CT-derived LBM decreased from 55.2±11.8kg pre-therapy to 49.27±9.84kg post-radiation. Methods comparison revealed 95% limit of agreement of ±12.5-13.2kg between CT and height-weight formulae. Post-treatment LBM with the three formulae was significantly different from CT (p<0.0001). In all instances, no height-weight formula was practically equivalent to CT within±5kg.

CONCLUSION: Formulae cannot accurately substitute for direct quantitative imaging LBM measurements. We therefore recommend CT-based LBM assessment as a routine practice of head and neck cancer patient body composition.