Many cancer patients undergoing radiation treatment or chemotherapy keep their use of complementary or alternative medicines secret from their oncologists, an omission that could compromise treatment, according to a survey.

A survey of 273 patients at Philadelphia cancer clinics and Internet responders found that 48% of patients hedge their bets with alternative or complementary products, and about 75% of them do not divulge this to their doctors.

Of the radiation patients, 35% used complementary or alternative medicines, researchers reported at the American Society for Therapeutic Radiology and Oncology meeting here. Of those receiving chemotherapy, 65% used complementary or alternative products.

The study included 142 patients getting radiation therapy for either breast or Prostate cancer, and 131 chemotherapy patients, said Neha Vapiwala, M.D., a radiation oncology resident at the University of Pennsylvania in Philadelphia.

“When we give patients radiation therapy, we want the radiation to create free radicals that destroy tumor cells,” Dr. Vapiwala said in a poster presentation. “But herbal medications such as saw palmetto and St. John’s Wort contain antioxidants that may prevent what we want the radiation to accomplish.”

Dr. Vapiwala said that all patients undergoing radiation therapy are advised to stop taking all alternative or complementary medications except for a once-daily standard vitamin pill. They are specifically asked to stop high doses of vitamins. “We really don’t know what these products do to our patients undergoing radiation, so we think the best answer - until they are thoroughly studied - is not to use them,” she said.

The survey respondents suggested that they used the non-prescription products as a cost-effective means of treating their cancer. On average, patients used two different products, with vitamins, herbal supplements, and botanical supplements being the most common.

According to Dr. Vapiwala, patients who used these products tended to have a higher educational level, reflecting possible higher income to purchase the supplement, as well as access to the Internet and other publications.

It’s important for doctors to know about their patients’ use of complementary or alternative medicines and to understand patients’ reasons for using them, Dr. Vapiwala said. In this way, physicians can better tailor treatment regimens and improve patients’ quality of life.

Dr. Vapiwala advised doctors to be more open with patients about these medicines so the patients will discuss them in detail. Also, she added, ask patients about the medications throughout the treatment period. “A one-time question is not enough.”

“This is a problem most of us don’t know how to deal with,” said Gregory Swanson, M.D., an associate professor of radiation oncology and urology at the University of Texas at San Antonio. “You name a product, and some of our patients have taken it.”

The use of complementary or alternative medicine is not benign, Dr. Swanson said, adding that he has had patients who have succumbed to fatal doses of Vitamin A because they thought megadoses would help fight their cancer.

“There may be something out there that works,” he said, noting that drugs such as Taxol (paclitaxel) are derived from bark of trees. “But for many of these products, we just don’t know how they may interfere with treatment. “I have advised my patients not to take these medicines for that reason.”

Source: American Society for Therapeutic Radiology and Oncology 47th annual meeting