Regular consumption of caffeinated coffee may help prevent the return of colon cancer after treatment and improve the chances of a cure, according to a new, large study from Dana-Farber Cancer Institute that reported this striking association for the first time.

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 34 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 Charles S. Fuchs, MD, MPH, director of the Gastrointestinal Cancer Center at Dana-Farber. First author is Brendan J. Guercio, MD, 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.

"We found that coffee drinkers had a lower risk of the cancer coming back and a significantly greater survival and chance of a cure," Fuchs said.

Most recurrences happen within five years of treatment and are uncommon after that, he noted.

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.

Fuchs said these patients have about a 35 percent chance of recurrence.

As encouraging as the results appear to be, Fuchs is hesitant to make recommendations to patients until the results are confirmed in other studies.

"If you are a coffee drinker and are being treated for colon cancer, don't stop," he said.

"But if you're not a coffee drinker and wondering whether to start, you should first discuss it with your physician."

Fuchs said 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.

Fuchs said 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 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, Fuchs said.

Other than drinking coffee, Fuchs said, people can take other measures to reduce cancer risks – avoiding obesity, exercising regularly, adopting a healthier diet, and eating nuts, which also reduce the risk of diabetes.

Source: Dana-Farber Cancer Institute