Fractionated irradiation combined with carbogen breathing and nicotinamideof two human glioblastomas grafted in nude mice

This study addressed the potential radiosensitizing effect of nicotinamide and/or carbogen on human glioblastoma xenografts in nude mice. U-87MG and L N-Z308 tumors were irradiated with either 20 fractions over 12 days or 5 fr actions over 5 days in air-breathing mice, mice injected with nicotinamide, mice breathing carbogen, or mice receiving nicotinamide plus carbogen, The responses to treatment were assessed using local control and moist desquam ation. In U87MG tumors, the enhancement ratios (ERs) at the radiation dose required to produce local tumor control in 50% of the treated mice (TCD50) with nicotinamide and/or carbogen ranged from 1.13 to 1.24 for irradiation in 20 fractions over 12 days. In LN-Z308 tumors, the ERs at the TCD50 with nicotinamide and/or carbogen ranged from 1.22 to 1.40 for irradiation in 5 fractions over 5 days and from 1.11 to 1.30 in 20 fractions over 12 days, r espectively, Skin injury was slightly enhanced, with ERs ranged from 1.06 t o 1.15 when radiation was combined with carbogen and/or nicotinamide, Thus carbogen and nicotinamide can slightly improve the radiation response of hu man glioblastoma xenografts, (C) 2001 by Radiation Research Society.