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More than 80 percent of women who are at high risk of developing breast cancer don’t take medications that could prevent it.

No kind of cancer is more common in women than breast cancer. Every year, worldwide, over 2.7 million women are diagnosed with breast cancer, and over 500,000 women die of it. In Western countries, one in eight women will eventually be diagnosed with the disease, although the risk is lower for women in other parts of the world.

Until the 1990’s, there was very little women could do to prevent breast cancer other than to pursue a healthy lifestyle and hope for the best. With the advent of selective hormone receptor modulators, however, breast cancer prevention has become possible, although it’s not a perfect process.

What Is a Selective Hormone Receptor Modulator?

Many, although not all, breast cancers are fueled by hormones. When breast cancer tumors are removed, they are biopsied to determine whether the cancer is:

  • Endocrine receptor positive, that is, having receptor sites for either estrogen or progesterone, or both, which stimulate the growth of tumors,
  • HER2 positive, having receptor sites for a growth factor that also stimulates growth of tumors,
  • Triple-receptor positive, having receptor sites for estrogen, progesterone, and HER2, or
  • Triple-receptor negative, having no receptor sites for any of the three tumor growth factors.

In some women estrogen, progesterone, and/or HER2 stimulate the growth of cancer. Blocking the action of estrogen, progesterone, and/or HER2, in those women, blocks the growth of cancer. Receptor blockers won’t have any effect in women who don’t have the receptors, but in some women, they could make a huge difference in the risk of recurrence of cancer. To that end, pharmaceutical companies have developed:

  • Tamoxifen, also known as TMX and marketed under the trade name Nolvadex, to block estrogen receptors. Another drug called fulvestrant (marketed as Faslodex) at first blocks the estrogen receptor and then destroys it.
  • Megestrol acetate (Megace) to block progesterone receptors.
  • A monoclonal antibody trastuzumab (marketed as Herceptin) to block HER2 receptors.

All of these treatments have been around for about 25 years. They are well known, and their cost has been greatly reduced. Many health insurance programs, even in the United States, cover them for women who have had breast cancer treatment.

How Well Do Drugs for Breast Cancer Prevention Work?

These drugs are typically given to prevent a recurrence of breast cancer, rather than the first appearance of the disease. In women who have been treated for breast cancer in the past:

  • About 60 percent of women whose tumors were estrogen- or progesterone-receptor positive have a partial or complete response to tamoxifen. (It won’t help women who are triple-receptor negative.)
  • Megace helps up to 90 percent of women who have had breast cancer maintain appetite and avoid wasting. This indirectly extends life.
  • Herceptin prolongs life in about 93 percent of women who use it, and it prevents return of the cancer in about 74 percent, although it can cause severe heart damage if it is used for longer than one year.

Why Do Women Reject Potentially Life-Saving Treatments?

“Severe heart damage” resulting in congestive heart failure is a significant impediment to successful treatment with any drug. Similar side effects discourage women from using most of the medications that, in many cases, extend life or even lead to long-term remission from breast cancer. However, when researchers ask women why they don’t take cancer-preventive medication, their answers tend to be:

  • Doctor recommendations are taken seriously, but they have to be delivered in the right way.
  • Women find out about side effects their doctors failed to mention by searching on the Internet, and become skeptical of the quality of their care.
  • Doctors fail to be specific about the risks and benefits of treatment, what are the odds of success, what are the odds of side effects, how much does a treatment add to both quality of life and length of life.

  • Women often don’t feel “empowered” to ask questions, although making sure the patient gets enough information is primarily the doctor’s responsibility, not hers.
  • Women who know they have BRCA mutations look to mastectomy (and oophorectomy, removal of the ovaries) as primary prevention of cancer.
  • Women who already experience hot flashes are less likely to start an estrogen sequestering medication like Tamoxifen, which can cause hot flashes.
  • Women  who want estrogen therapy, understandably, are less likely to opt for estrogen-sequestering drugs.
  • Any form of treatment that requires more visits to the doctor is likely to be rejected.

On the other hand, starting cancer prevention drugs does not seem to depend on whether or not a woman has passed menopause, what kind of job she has, the number of children a woman has had, or, surprisingly, insurance status.

Once women start cancer prevention therapies, about 60 percent continue them for more than six months. Women who are more likely to stick to their cancer prevention programs:

  • Tend to have achieved higher educational levels.
  • Usually do not smoke.
  • Often pursue other, alternative methods of cancer prevention (diet, herbs, alternative therapies).
  • Are less depressed about having had cancer or having had a mastectomy. Women who are more depressed are more likely to drop out of treatment.
  • Women who regard Tamoxifen, Megace, or Herceptin as “cancer drugs” that remind them or their families of cancer are less likely to stay on their treatments.
  • Women who are skeptical of medication in general are less likely to complete a course of treatment.

Income, insurance status (possibly because so many of the studies of the subject were conducted in Europe), the number of children at home, menopause status, marital status, and living alone seem to have little or no effect on how long women stick to their treatment programs. Very few women, less than 14 percent, however, stay on Tamoxifen, Megace, or Herceptin longer than three years. Eventually, most women drop out of treatment.

Doctors need to realize that their “orders” are not necessarily obeyed. Women who want to beat cancer should make every effort to be fully informed of their options and their opportunities for success.

Sources & Links

  • Smith SG et al. Factors affecting uptake and adherence to breast cancer chemoprevention: A systematic review and meta-analysis. Annals of Oncology Advance Access published December 8, 2015.
  • Photo courtesy of komunews: www.flickr.com/photos/komunews/10317589276/
  • Photo courtesy of Arturo de Albornoz:https://www.flickr.com/photos/liveu4/2011237087/

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