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Wednesday, 19 August 2015
The patients, all of them treated with surgery and chemotherapy for stage III colon cancer, had the greatest benefit from consuming four or more cups of coffee a day (about 460 milligrams of caffeine), according to the study published in the Journal of Clinical Oncology. These patients were 42 percent less likely to have their cancer return than non-coffee drinkers, and were 33 percent less likely to die from cancer or any other cause.
Two to three cups of coffee daily had a more modest benefit, while little protection was associated with one cup or less, reported the researchers, led by Dr. Charles Fuchs, director of the Gastrointestinal Cancer Center at Dana-Farber. First author is Dr. Brendan J. Guercio also of Dana-Farber.
The study included nearly 1,000 patients who filled out dietary pattern questionnaires early in the study, during chemotherapy and again about a year later. This "prospective" design eliminated patients' need to recall their coffee-drinking habits years later -- a source of potential bias in many observational studies.
Researchers say they found that coffee drinkers had a lower risk of the cancer coming back and a significantly greater survival and chance of a cure. Most recurrences happen within five years of treatment and are uncommon after that, they note. In patients with stage III disease, the cancer has been found in the lymph nodes near the original tumour but there are no signs of further metastasis. Researchers say these patients have about a 35 percent chance of recurrence.
As encouraging as the results appear to be, researchers are hesitant to make recommendations to patients until the results are confirmed in other studies.
Dr. Fuchs says the study is the first to study an association between caffeinated coffee and risk of colon cancer recurrence. It adds to a number of recent studies suggesting that coffee may have protective effects against the development of several kinds of cancer, including reduced risks of postmenopausal breast cancer, melanoma, liver cancer, advanced prostate cancer. According to Dr. Fuchs the research focused on coffee and other dietary factors because coffee drinking -- in addition to possibly being protective against some cancers -- had been shown to reduce the risk of type 2 diabetes. Risk factors for diabetes -- obesity, a sedentary life style, a Western diet high in calories and sugar, and high levels of insulin -- are also implicated in colon cancer.
In analysing the results of the new study, Fuchs and his colleagues discovered that the lowered risk of cancer recurrence and deaths was entirely due to caffeine and not any other components of coffee. He said it's not clear why caffeine has this effect and the question needs further study. One hypothesis is that caffeine consumption increases the body's sensitivity to insulin so less of it is needed, which in turn may help reduce inflammation -- a risk factor for diabetes and cancer.