Effect of radiotherapy on plasma and tumour ascorbic acid levels

In 21 patients plasma ascorbic acid levels were estimated sequentially during their course of radiotherapy. These levels were found to decline from a mean of 0.5 mg/dl to 0.3 mg/dl during a typical course of radiotherapy. This effect was more noticeable for therapy to abdominal sites than other areas, such as the head or neck. In a separate study of 16 patients with accessable tumours, the tumour ascorbic acid levels were estimated sequentially during a course of radiotherapy. These levels increased during therapy from a mean of 11.5 mg/ 100 g to 14.5 mg/100 g. The likely explanation of these observations is discussed and their implications explored in view of recent indications that vitamin C may exert a radioprotective effect.