Taking vitamin E doesn't protect head and neck cancer patients from developing new tumors, Canadian researchers report. In fact, it may actually raise the risk of developing a second cancer.

The study, published in the Journal of the National Cancer Institute (Vol. 97, No. 7: 481-488), is the second recent piece of research to cast doubt on the use of vitamin E against cancer. Just last month a team of international researchers said vitamin E supplements don't offer any protection against cancer but may well raise the risk of heart failure in some patients.

The new study, led by researchers at L'Universite Laval in Quebec, involved 540 patients with stage 1 or 2 head and neck cancer (oral cavity, pharynx and larynx). During radiation therapy and for 3 years after, half the patients took daily vitamin E supplements (400 IU, or international units), while the other half took a placebo. (Some of the vitamin E patients were also given beta carotene supplements, but these were stopped after about 1 year, when another study showed beta carotene could increase the risk of lung cancer in smokers.)

People who took the vitamin E had a significantly higher rate of second cancers than people who took the dummy pill. In the years they were taking the pill, vitamin E appeared to more than double the risk of developing a second cancer. Once they stopped, however, their rate of second cancers was lower than that of people on the placebo. And after 8 years of follow up, the rate of second cancers in both groups was the same. The rates at which the initial cancers came back followed the same pattern.

"Nevertheless," the researchers wrote, "our results suggest that caution should be advised regarding the use of high-dose [vitamin E] supplements for cancer prevention."

The results came as a bit of a surprise, they observed, because some earlier studies had suggested a lower rate of new cancers in groups taking vitamin E. Instead, they said, the vitamin E appeared to speed up the progression of cancer.

In an editorial published in the same issue of the journal, two head and neck cancer specialists from M.D. Anderson Cancer Center in Houston said there is still hope of finding a substance that helps prevent new cancers in these patients.

However, they said future studies must use genetic clues called biomarkers to carefully select a substance that's likely to have an effect against this type of cancer, and to find the patients most likely to benefit from it.