The predictive value of body protein for chemotherapy-induced toxicity

The use of body surface area in determining chemotherapy dosing, particularly in the obese, remains controversial. Total body nitrogen (TBN) measurement in patients with serious illness has been suggested to be an accurate predictor of clinical course. The ability of TBN to predict chemotherapy-induced neutropenia was examined in the current study.

TBN measurements were performed in 31 female outpatients with breast carcinoma who were undergoing standard cyclophosphamide, methotrexate, and 5-fluorouracil (CMF)-based chemotherapy (median age, 48 years; range, 26- 77 years). TBN was measured using the in vivo neutron capture analysis technique on Day 1 of Cycles 2-6. The chemotherapy toxicity index used was the absolute neutrophil count nadir (ANCN). Neutropenia was defined as an ANCN < 1.0 x 10(9)/L. The nitrogen index (NI) (TBN expressed as a percentage of age-, gender-. and height-matched healthy patients) then was compared with the corresponding ANCN values.

Using receiver operating characteristics analysis, a "cut-off" value of NI = 0.89 was found. In this group of patients, when the NI was < 0.89, 11 of 13 courses in 7 patients (85%) led to an ANCN of < 1.0 x 10(9)/L, and when the NI was > 0.89, 29 of 109 courses (27%) led to an ANCN of < 1.0 x 10(9)/L (P < 0.0001).

In this small group of breast carcinoma patients, the NI was found to be the most powerful predictor of neutropenia after CMF-based chemotherapy. The authors conclude that NI may be a useful clinical tool in identifying patients at a higher risk of chemotherapy-induced toxicity when widely distributed drug combinations such as CMF are used, and warrants further study with other commonly used drugs or drug regimens.