ACUTE EFFECTS OF ACCELERATED RADIOTHERAPY IN COMBINATION WITH CARBOGEN BREATHING AND NICOTINAMIDE (ARCON)

Combining accelerated radiotherapy with carbogen and nicotinamide (NAM ) has been proposed as a strategy to overcome the sparing effect of tu mour clonogen repopulation and hypoxia. Six patients with squamous cel l carcinomas of the head and neck were given accelerated radiotherapy, carbogen breathing and high dose nicotinamide in order to evaluate th e feasibility of this treatment regimen. The patients received radioth erapy in two daily fractions of 1.8-1.9 Gy, five days/week, total dose 54-57.6 Gy, in an overall treatment time of 19-22 days. The interfrac tion intervals were 7-8 hours between the two fractions on the same da y. Carbogen breathing was started 5 minutes before and went on during each radiation fraction. A variety of NAM doses were administered oral ly in conjunction with radiation therapy and analyses of plasma concen trations of NAM and its metabolites were performed. The most common si de-effect from NAM was nausea and vomiting, which in one case hampered further NAM administration. The side effects were not related to plas ma levels of NAM or its main metabolites. Additionally, one patient wi th preexisting heart disease developed a severe hypotension and renal dysfunction. AU acute reactions healed without further complications. The mucosal reactions were generally brisk. Thus, the combination of a ccelerated radiotherapy with carbogen and NAM seems to be tolerable.