540 Activity of liver monooxygenases in pediatric oncological patients

Abstract

Liver monooxygenases (LMO) metabolize most antitumor drugs and LMO activity is a factor determining their efficacy. For example, anticancer agents are less active and more toxic in patients (pts) with concomitant hepatic damages which result in inhibition of LMO activity. The question is how many pts have low LMO activity. We examined 146 pediatrie oncological pts without hepatic pathology by determining half life-time of antipyrin (Tl/2 AP). Only 22% pts had high LMO activity, the same as in healthy (Tl/2 AP is 5h and less). 46% pts had moderate LMO activity (Tl/2 AP is 5–10h) and 32%—low LMO activity (Tl/2 AP is more than 10h). Among 36 pts with concomitant hepatic damages the latter group included 63% pts. So about 1/3 of all pts and 2/3 of the pts with hepatic damages cannot achieve optimal effect of chemotherapy regardless of tumor sensitivity. We believe to optimize the drug efficacy LMO inhibited activity should be stimulated to the normal level before chemotherapy and we have already had positive results of the approach.