Breast Cancer Prevention Drug Approved
The Food and Drug Administration approved Thursday the use of tamoxifen as the first drug to prevent breast cancer in healthy women at very high risk of developing the disease.
But the drug, which has long been a potent treatment for already diagnosed breast cancer, can have potentially serious side effects. Women at significant risk for developing breast cancer will have to decide which threat is greater--and whether it is worth the gamble to start taking the drug when they are still healthy, the FDA said.
“This is not a simple, straightforward decision but calls for a fairly sophisticated choice,” said acting FDA Commissioner Michael Friedman. “We know that tamoxifen has real serious side effects and that not all women who take it get benefits from it. But we do know that some women at high risk have a very meaningful reduction in that risk.”
The agency stressed that a woman’s decision to take the drug must be made carefully in consultation with her physician, taking multiple risk factors into account.
‘Extraordinary Optimism’
Chief among tamoxifen’s side effects is a higher-than-average chance of developing uterine cancer and blood clots of the major veins and lungs.
Despite these dangers, the approval “brings us such extraordinary optimism,” said Susan Braun, president of the Susan G. Komen Breast Cancer Foundation. “While there are still unanswered questions, there is a huge potential in this when you compare it to other measures of progress in the fight against breast cancer.”
Friedman agreed, calling the action “really exciting, that there are interventions that can reduce the risk of a common cancer like breast cancer--that’s a very important step to build upon.”
But Cynthia Pearson, executive director of the National Women’s Health Network, criticized the FDA action as “premature,” saying that it is based on the results of only one study and warning that there is insufficient information about the drug’s long-term effects.
The drug is made by Zeneca Pharmaceutical Inc. of Wilmington, Del.
As a treatment, tamoxifen slows or stops the growth of cancer cells. Researchers first saw its potential as a preventive medication when it seemed to prevent the development of new cancers in a woman’s noncancerous breast.
The drug works in breast tissue by interfering with estrogen, the female hormone that promotes the growth of breast cancer cells.
Breast cancer, which kills about 44,000 women annually, is the most commonly occurring cancer in women and the second-leading cause of cancer death among them, after lung cancer. About 180,000 new cases are diagnosed every year.
Breast cancer “accounts for 31% of all cancers among women. Today’s action provides an important new option for some women at heightened risk of breast cancer,” said Health and Human Services Secretary Donna Shalala.
Until now, women at high risk of developing breast cancer had but two choices: They could opt for a mastectomy while still cancer-free to try to avoid the disease or practice “watchful waiting” with the hope of catching the cancer if it did develop in its earliest stages.
Shown to Cut Chances of Cancer in Half
Tamoxifen, which has been used as a breast cancer treatment for more than 20 years, was shown in a recent study to cut a woman’s chances of developing the disease by nearly half. The drug did not completely eliminate the risk of developing breast cancer. Nevertheless, the results were so startling that researchers halted the trial 14 months early.
In September, an FDA advisory committee recommended that the agency approve its use as a breast cancer preventive agent but cautioned that only those seen as likely to get the disease consider taking it.
The agency emphasized that the drug should be prescribed only for those women at very high risk.
Factors that raise a woman’s risk of breast cancer include the number of first-degree relatives (mothers, daughters, sisters) who have had breast cancer; having no biological children; and giving birth to a first child when older than 30. It also includes those who have a history of noncancerous breast lumps, atypical cell clusters and lobular carcinoma in situ--a noninvasive, or localized, breast cancer--which makes a woman nine times more likely to develop invasive breast cancer.
Also, being older than 60 makes a woman five times more likely to develop breast cancer than women in the earlier age group of 35 to 39.
Tamoxifen should not be taken for longer than five years because there is no information about benefits after that period of time and extended use raises concerns about increasing the chances of other side effects, the FDA said.
For those women uncertain about taking the drug, “the physician . . . can be a very, very important partner, particularly for a woman who doesn’t know what questions to ask and who needs help assessing her risk,” Friedman said.
The pivotal study that helped the drug win FDA approval was launched before the discovery of breast cancer gene alterations, known as BRCA1 and BRCA2, which increase a woman’s risk of breast cancer. Researchers have begun analyzing blood samples from study participants to identify women with these alterations and to determine whether the drug has had the same effects on them.
Friedman said that researchers would continue to follow the progress of women on the drug, and “as we get more information we’ll be able to refine some of the unknown things.”
The study used a computer model, called the “Gail Model,” to identify women at very high risk. Recognizing that not all health care providers have access to this model, the FDA said that the drug manufacturer would provide comprehensive materials to doctors to help them in calculating patients’ risk.
Also, the agency said that new labeling would spell out risk factors in detail to assist physicians and women in their decision-making.
Last week, the government announced that it would launch another breast cancer prevention trial of tamoxifen versus another drug, raloxifene, which is used to treat osteoporosis but may also have effects in combating breast cancer.
