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Ask Dr. Block
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Gastric Cancer: Diet and Xeloda
Question: In Life Over Cancer, you recommend a modified macrobiotic diet or low fat, few animal proteins, high vegetable, no refined carbs, to best make the body inhospitable to cancer. You cite the benefits of the Japanese diet. Is this true with gastric cancer, too? I understand that gastric cancer is prevalent in Japan.
Also, you say that antioxidants taken during treatment on Xeloda enhanced treatment effectiveness. Would this be expected for gastric cancer treatment with Xeloda as well?
Answer: Gastric cancer occurs at higher rates in Japan and Korea than in the United States. It also occurs at high rates in impoverished populations in Latin America and Africa. A key diet characteristic of Japan and Korea that may be associated with gastric cancer is the high prevalence of salted, smoked and pickled vegetables in the diet, although this is not entirely certain. Salted foods are used to a much greater extent in these countries than in the United States. They are used to a small extent in the American version of the traditional Asian diet, macrobiotics. I do not recommend use of highly salted foods, smoked foods or pickles in large amounts in the Life Over Cancer diet. In fact, you should stay away from such foods as much as possible. Use of fresh vegetables and fruits is what you should concentrate on. The high incidence of gastric cancer in impoverished populations is somewhat of a different question. One possibility is, of course, the lack of refrigeration, which means that the availability of fresh vegetables and fruits may be quite variable in different seasons. This could lead to periods where the stomach is not protected by the phytochemicals in fresh produce.
But an over-riding factor in the Asian, Latin American and African populations could be the high incidence of infection with carcinogenic strains of the bacterium Helicobacter pylori (H. pylori) which causes stomach ulcer and other inflammatory diseases of the stomach. These diseases can give rise to stomach cancer. There may be some genetic characteristics in the Asian populations, as well, that make them particularly susceptible to carcinogenic damage from these bacteria. The United States and Europe are lucky enough not to have a high incidence of such dangerous strains, although infection with H. pylori does contribute to gastric cancer in these areas as well. Other causative factors for gastric cancer that may be more common in the Western countries include smoking, family history, lack of physical activity and obesity.
Xeloda is an oral form of the drug 5-fluorouracil or 5-FU. 5-FU is not one of the drugs that kill cancer cells through a free radical mechanism. In our literature review of all the studies in which antioxidants were given with chemotherapy drugs, we looked for studies of drugs that use free radical mechanisms to kill cancer cells, since it is these drugs that some doctors think could be adversely affected by antioxidants. Because 5-FU is not one of the free radical drugs, we did not look for data on this drug in our study, since one would not expect antioxidants to inhibit its mechanism of cancer-killing. Interestingly, though, our literature review did retrieve 2 studies in which 5-FU was given with other drugs that do act through free radical mechanisms; one study used an oral form of the drug similar to Xeloda. In both these studies the antioxidant glutathione was given with chemotherapy to one randomly assigned group of patients, while the other group did not receive glutathione. In one study, the glutathione group had higher rates of complete disappearance of tumor (76% vs 52%) and lower rates of neurotoxicity (caused by the other drug in the study regimen) than the comparison group. In the other, the rates of tumor disappearance were similar but the glutathione group had less toxicity. We don’t have specific data on the regimen that you might be using, although some current chemotherapy regimens do pair Xeloda with free-radical acting chemotherapy drugs such as cisplatin. Our study didn’t find evidence from clinical studies that indicated antioxidants would interfere with the effectiveness of the free-radical acting chemo drugs. We specifically looked for studies of antioxidants and Xeloda to update our data, since our literature review was done a few years ago. We didn’t find any controlled studies about Xeloda and antioxidant agents.
References:
Kim HJ, Lim SY, Lee JS et al. Fresh and pickled vegetable consumption and gastric cancer in Japanese and Korean populations: a meta-analysis of observational studies. Cancer Sci. 2010 Feb;101(2):508-16.
Block KI, Koch AC, Mead MN. Impact of antioxidant supplementation on chemotherapeutic efficacy: a systematic review of the evidence from randomized controlled trials. Cancer Treat Rev. 2007 Aug;33(5):407-18
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Keith I. Block, M.D.
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