Patients with colon cancer who used multivitamins during and after being treated with post-surgical chemotherapy did not reduce the risk of the cancer returning or their dying from it, according to researchers at Dana-Farber Cancer Institute.

In a study of patients with stage III colon cancer - characterised as cancer in the large bowel area with some cancer cells in a few nearby lymph nodes - the researchers found that while multivitamin use had no beneficial effect on patients' outcomes, it also did not have a detrimental effect.

The findings are reported online in the Journal of Clinical Oncology and later will be published in a print edition.

Dr Kimmie Ng, the paper's first author and a gastrointestinal oncologist at Dana-Farber, said that despite conflicting evidence on the efficacy of multivitamins to reduce cancer risk and death, studies suggest that approximately 30 percent of Americans take multivitamins to prevent and treat chronic diseases such as cancer.

Among cancer survivors, between 26 and 77 percent report using multivitamins.

"With such a high proportion of cancer patients utilising multivitamin supplements in the belief that it will help them fight their cancer, we felt it was important to really examine the data to see what impact multivitamins had on cancer recurrence and survival," said Ng.

The researchers used two questionnaires to track multivitamin use during and after chemotherapy.

Of the 1,038 patients who completed the first survey, nearly half (518) responded they used multivitamins while receiving chemotherapy.

Of the 810 cancer-free patients who completed the second survey six months after chemotherapy, more than half (416) reported multivitamin use.

Ng and her colleagues found no statistically significant differences in the rates of disease-free survival (the study's primary endpoint), recurrence-free survival, or overall survival between those who used multivitamins and those who didn't.

They also determined that an array of factors, including socio-economic status, household income, multivitamin and individual vitamin dosage, and consistency of multivitamin use did not impact their findings.

However, they did find a small beneficial association between age and weight and the use of multivitamins while receiving chemotherapy.

Those 60 and younger experienced some survival benefit, as did obese patients. There were no benefits for either subgroup when the multivitamins were taken after chemotherapy was completed.

Ng said additional studies are needed to confirm their findings and to investigate whether there were other factors that influenced the outcomes.

"This study adds to a growing body of research that questions the purported benefit of multivitamin use, and it underscores the need to investigate the use of individual vitamins, such as vitamin D, which may, in fact, provide real benefit," said Dr Charles Fuchs, director of gastrointestinal oncology at Dana-Farber and the paper's senior author.

He noted that the average multivitamin typically contains only a small to modest amount of vitamin D.

Source: Dana-Farber Cancer Institute