Oct. 17, 2005 (Denver) -- About half of people with cancer undergoing radiation and/or chemotherapy may be taking vitamins, herbs, or other complementary medicines that could compromise their treatment, Pennsylvania researchers report.
Making matters worse, three in four of these people don't tell their doctor that they are taking them, says Neha Vapiwala, MD, a radiation oncologist at the University of Pennsylvania in Philadelphia.
Had their doctors known about the supplements, "most would take a conservative approach and ask patients not to take them during their treatment," she says.
The reason: In many cases, doctors simply don't know how vitamins or herbs will affect the cancer therapy, Vapiwala tells WebMD.
Gregory Swanson, MD, a radiation oncologist at the University of Texas Health Science Center at San Antonio, agrees.
"It's important to ask patients about complementary therapies," he says. "The problem is that most of us don't know what to do with the information as most of these therapies have never undergone rigorous scientific testing.
"To be conservative, I ask patients not to take supplements during treatment even if they want to start them again afterward," Swanson tells WebMD.
Vitamin, Herbal, Botanical Supplements Most Popular
The survey, presented here at the annual meeting of the American Society for Therapeutic Radiology and Oncology, included 487 people undergoing radiation or chemotherapy or both for a variety of cancers, including breast, prostate, and lung. Participants were asked whether they took complementary treatments, why they took them, and whether they thought they were helping.
The participants filled out the surveys either at Philadelphia-area clinics or over the Internet. Among the findings:
- Overall, 48% said they were using at least one type of complementary or alternative treatment; of them, 75% said their doctor didn't know about it.
- Use was not based on ethnicity or education level.
- Vitamin, herbal, and botanical supplements were the most popular treatments.
- Women were more likely to take the supplements than men: 52% vs. 42%.
- The most common reason for taking supplements after a diagnosis of cancer was "general overall health," cited by 40% of respondents.
- 80% of those surveyed thought the supplements were worth the cost. "Some were spending over $50 a month. Yet even people who weren't sure the supplements were helping thought they were worth the cost," Vapiwala says.
- Only about one-third of people taking complementary medicines cited their health care providers as primary sources of information on the supplements. "Their primary source of information was usually the Internet, other cancer patients, or family or friends," she says.
- People undergoing chemotherapy alone were more likely to use complementary treatments than people undergoing radiation alone: 65% vs. 35%.
How Supplements Might Compromise Cancer Treatment
Vapiwala offers one example of how high-dose supplements might compromise treatment. "Radiation works by creating free radicals that oxidize and kill both cancer and healthy cells," she says. "And lab studies suggest that antioxidants counter the effects of the oxidation process. "So while high-dose antioxidants might help prevent cell injury in a healthy person, they may be countering the effects of the radiation on unwanted cancer cells," she says.
Antioxidant supplements include beta-carotene and vitamins A, C, and E.
Vapiwala says many doctors don't ask their patients about complementary medicine and even if they do ask once, they often fail to follow up.
Also, people with cancer "often feel their doctors dismiss the benefits of complementary medicine so they are shy about sharing the information," she says.
So what should people with cancer be doing?
"Don't rely on your doctor, who may be in and out of the room, to bring it up," Vapiwala says. "Tell them what you are taking and how much."
Even better, bring in the bottles, she says. If you can't approach your doctor, share the information with a nurse, therapist, or other person at the clinic, she says.
Taking a daily multivitamin during treatment is fine, Vapiwala adds. "But stay away from the mega-doses."