INFLUENCING PHYSICIANS' DECISIONS

Pharmaceutical companies currently spend upwards of $10 billion per year in the US on inducements such as gifts, speaker's fees, free drug samples, subsidized travel and sponsored educational symposia, in an effort to influence the prescribing habits of the nation's physicians. Many studies have shown that these efforts pay off handsomely.

Industry pressure starts early in a doctor's career. Even while they are still in medical school, physicians-in-training have regular encounters with pharmaceutical company representatives. Such encounters are generally facilitated and sanctioned by the medical schools themselves.

It is encouraging to see that today's medical students are aware of this insidious pressure, and are fighting back. In 2003, the American Medical Student Association launched its Pharm Free campaign, aimed at encouraging academic medical centers to limit the access of pharmaceutical company representatives to medical schools, and preventing faculty and students accepting gifts from industry representatives.

Another admirable group is No Free Lunch, a non-profit organization of doctors, medical students and other healthcare professionals who oppose the influence of the pharmaceutical industry on medical practice. One of the group's guiding principles is that pharmaceutical promotion should not influence medical practice. "Our mission is to encourage health care providers to practice medicine on the basis of scientific evidence rather than on the basis of pharmaceutical promotion," says the organization's Web site (www.nofreelunch.org).

Unfortunately, this activism has not been uniformly well received within the medical profession. The American Academy of Family Physicians (AAFP), for example, which is one of the largest professional groups within US medicine, refused to rent space to No Free Lunch at the 2005 AAFP annual assembly - but did rent space not only to representatives of many pharmaceutical companies, but also to McDonald's, the fast food company whose influence on the American diet has, to say the least, been far from beneficial.

CALCIUM SUPPLEMENTS COMBAT BONE METASTASES IN MICE

Could a glass of vitamin-fortified milk per day block the spread of cancer to the bones? According to researchers at the University of Sydney, Australia, this may be the case, at least in animals. Senior author Colin R. Dunstan, PhD, and his colleagues theorized that since a strong skeleton is less receptive to metastasizing cancer cells, dietary calcium might help prevent the spread of cancer to bones.

Dr. Dunstan and his team used a mouse model of breast cancer metastasis and found that a simple calcium deficiency increased the tendency of breast cancer to go to bone. Their findings were published in the Oct. 1, 2007 issue of Cancer Research (Zheng 2007).

Some cancers are particularly likely to spread to bone. About 70 percent of advanced breast cancer patients, for example, develop secondary (metastatic) tumors in the bone. When cancer spreads to the skeleton it breaks down existing bone, often leading to pain and limitation of mobility. In addition, the very process of bone breakdown that allows these secondary cancers to become established may also make the bone significantly more receptive to further metastatic spread. Dunstan called this a "vicious cycle," in which the bones become increasingly fertile ground for further metastases.

The Sydney researchers compared the effects of low- and high-calcium diets in mice. They found that dietary calcium deficiency was related to a higher rate of cancer cell proliferation as well as to an increase in the proportion of bone colonized by the spread of secondary cancer. This seems like common sense, but it is a perspective that has rarely been articulated by the medical profession.

"These results could have implications for patients with breast cancer bone metastases or who are at high risk for developing metastatic disease," Dunstan said. "Many older women in our community are known to be calcium deficient due to low calcium dietary intake or due to vitamin D deficiency. These women could be at increased risk for the devastating effects of bone metastases."

Vitamin D is required for the proper uptake of calcium. For more information on this important vitamin, see www.vitamindcouncil.com and www.sunarc.org

The Australian scientists concluded that increased bone turnover, due to dietary calcium deficiency, promotes tumor growth in bone. Breast cancer patients frequently have low dietary calcium intake and high bone turnover.

Dr. Dunstan has called for clinical trials "to investigate how calcium and vitamin D status influence progression to metastatic disease, and to determine if corrections of calcium and vitamin D deficiencies are important in breast cancer patients."

A clinical trial is underway in the US to investigate the role of oral calcium supplements and vitamin D in preventing or delaying bone-related symptoms in patients with bone metastases from cancers of the prostate, lung or breast. Calcium supplements and vitamin D are given alongside the bone-seeking drug zoledronate, and in addition to either strontium 89 or samarium 153. While this study may not answer all the questions raised by the Dunstan article, it is a start. But it will be difficult to parse the contribution of vitamin D and orally ingested calcium from the final results.

What I would love to know is whether regular sun exposure, which is necessary for the production of vitamin D within the skin, can offer a significant contribution towards combating the spread of breast cancer to the bones. But although this study made no attempt to answer that question, it is certainly a good start.

Resource:

The clinical trial mentioned above is titled "Zoledronate, Vitamin D, and Calcium With or Without Strontium 89 or Samarium 153 in Preventing or Delaying Bone Problems in Patients With Bone Metastases From Prostate Cancer, Lung Cancer, or Breast Cancer." It was opened in August 2006, and is presently recruiting patients. The study chair is Michael J. Seider, MD, PhD, FACR, Akron City Hospital, Akron, OH, and there are study locations all over the US. Readers can find out more about eligibility requirements by visiting http://www.clinicaltrials.gov and entering the trial number (NCT00365105) in the search box.

References:

Zheng Y, Zhou H, Modzelewski JR, et al. Accelerated bone resorption, due to dietary calcium deficiency, promotes breast cancer tumor growth in bone. Cancer Res 2007;67:9542-9548.