A new report that looks at the environmental factors that affect risk of breast cancer is out. It suggests that women can reduce their risk by avoiding unnecessary medical radiation, forgoing hormone treatments for menopause that combine estrogen and progestin, limiting alcohol intake and minimizing weight gain.
Further, controlling weight appears helpful only in preventing postmenopausal breast cancers, not those in younger women. Overuse of CT scans, which deliver a relatively high dose of radiation, was a particular concern, but the report stated that women should not be deterred from having routine mammograms, which use a much smaller dose.
The 364 page report that took two years to draft was issued on Wednesday by the Institute of Medicine, an independent group that is part of the National Academy of Sciences and advises the government and public. The work was done by a committee of 15 outside experts, mostly from universities, and nine institute staff members. The sole sponsor was a breast cancer advocacy group, Susan G. Komen for the Cure, which requested the report and spent $1 million on it.
“In the last 20 years, the National Institutes of Health and private foundations have put a lot of money into trying to identify what are the risk factors for breast cancer,” said Irva Hertz-Picciotto, chairwoman of the expert committee and chief of environmental and occupational health at the University of California, Davis. “It’s a bit disappointing that so little has been learned with the amounts of money that have gone into it.” The committee could not “identify a bunch of environmental factors” like common chemicals, air and other pollutants etc. that might contribute to breast cancer, Dr. Hertz-Picciotto said.
Experts however claim that the problem is difficult to study for a number of reasons. Suspect chemicals cannot ethically be given to people to see if they cause cancer. People exposed in the past can be studied, but information about the dose and timing may be sketchy. Animal studies can provide useful information, but do not always apply to humans. And people are often exposed to mixtures of chemicals that may interact in complex ways, with effects that may also vary depending on an individual’s genetic makeup.
The report adds that women should exercise and avoid smoking to bring down their risk of breast cancer. The panel also found “possible associations” between breast cancer and secondhand smoke, nighttime shift work and exposures to the chemicals benzene, ethylene oxide and 1,3-butadiene, which are found in some workplaces, car exhaust, gasoline fumes and tobacco smoke. One such chemical is bisphenol A, or BPA, which is used in some plastic containers, can liners, food packaging and other products. It can mimic estrogen, which can feed the growth of some breast cancers.
Dr. Hertz-Piccioto said that women could try to avoid BPA, but must choose substitutes carefully to make sure they do not wind up exposed to something worse. The report also found that there was no evidence that personal use of hair dye increases risk. But they made no determination about possible risks to hairdressers, who may have regular, heavy exposure to the dyes. The report said more information was also needed about nail salon workers and consumers exposed to various manicure products, which contain multiple hazardous chemicals. Dr. Hertz-Picciotto said studies in women exposed to radiation during childhood found an increased risk of breast cancer and suggested that young girls may be particularly susceptible.
Elizabeth Thompson, president of Susan G. Komen for the Cure, said her organization was pleased with the report.
About 230,000 new cases of breast cancer, and about 40,000 deaths from the disease, are expected this year in the United States. In the next ten years, an estimated 24 of every 1,000 white women aged 50 or 2.4 percent, will be found to have breast cancer, and compared to 2.2 percent of black women, 2 percent of Asian women and 1.7 percent of Hispanic women.
Radiotherapy for breast cancer
In another study published Tuesday, it was noted that women who get a quicker, localized form of radiation treatment for early-stage breast cancer are more likely to need to have their breast removed later on than women treated with traditional radiation of the whole breast.
The study was released late on Tuesday at a breast cancer meeting in San Antonio, suggests the increasingly popular practice of using a quicker method known as known as accelerated partial breast irradiation therapy may be less effective than standard radiation.
“Our study compared the two radiation therapy techniques available to women with early-stage breast cancer,” said Dr. Benjamin Smith of the University of Texas MD Anderson Cancer Center, who worked on the study. He said women who were treated with the localized radiation technique have double the risk for needing a mastectomy within five years, either because a breast tumor came back or because of complications caused by the radiation itself.
The MD Anderson team studied a form of the rapid radiation treatment known as brachytherapy, in which radiation is administered to women through a catheter to kill breast cancer cells that might linger after surgery. It was first approved in 2002 and has become increasingly popular. The treatment is typically done a few days after a woman's tumor is removed. Patients are typically treated twice a day for five to seven days. More traditional radiation treatment can take five to seven weeks.
The study is based on analysis of Medicare claim forms from 130,535 beneficiaries nationwide, who were diagnosed with cancer between 2000 and 2007. “In our study of Medicare patients, we found a consistent increase in APBI brachytherapy, from less than 1 percent in 2000 to 13 percent in 2007. It's our guess that this trend has continued,” Smith said in a statement.
During the same eight-year period, about 4 percent of patients treated with brachytherapy underwent a mastectomy in the following five years, compared to only 2.2 percent of those treated with whole breast irradiation. In addition, brachytherapy was associated with a higher rate of infections, rib fractures, fat necrosis and breast pain.
Although the overall risks were low, the team said it is important for doctors to explain the potential risks and benefits of this treatment to their patients.
Chemotherapy for breast cancer
A new study from Oxford University that was recently published in the Lancet medical journal has shown that modern chemotherapy drugs are reducing breast cancer death rates.
The study included data from 123 trials conducted over the past four decades involving about 100,000 women. Findings showed that standard while chemotherapy treatments in the 1980s reduced breast cancer mortality by nearly one-quarter, the effectiveness of modern chemo drugs cut the death rates by about one-third when compared to patients not undergoing chemotherapy.
The positive impact was applicable to all women regardless of age, tumor size, level of spread, and whether or not the cancer was sensitive to estrogen. However, for ER-positive cancers, which are sensitive to estrogen, a combination of chemotherapy and hormone (endocrine) therapy was found to be more effective than hormone treatment alone.
New Lancet Commission on Breast Cancer: Transforming breast cancer care globally