Women in northern California’s Marin County are presently being diagnosed with invasive breast cancer at a rate approximately 40 percent higher than the officially recorded national average. In this affluent community the recorded incidence of the disease among white women aged 45 to 64 has increased by 72 percent during the last decade. Diagnoses of breast cancer for the entire female population climbed by 37 percent in the county during the last decade, compared with a 3 percent increase for the rest of the San Francisco Bay Area.

Researchers note that the increase in one year was particularly disturbing. “Between 1998 and 1999, there was a 20 percent increase in breast cancer in white, non-Hispanic women living in Marin County,” according to Janice Barlow, executive director of Marin Breast Cancer Watch, an organization formed by residents in 1995.

The area’s leading expert on the affliction, Christina A. Clarke, an epidemiologist at the Northern California Cancer Center, has compiled a profile of the high-risk group using census data and cancer registry information. The county’s 250,000 residents are predominantly white and households earn on the average more than $80,000, almost $30,000 above the national average. Ironically, in general this demographic group has better access to health care, which has led some researchers to speculate about the consequences of the higher usage of hormone replacement therapy, recently linked in some studies to breast cancer.

Clarke dismisses one of the notions circulating, that better access to medical care leads to more cancer screening and therefore more diagnoses. “If everyone was just getting a lot of mammography and they were catching it earlier, I think you would expect that the Marin women would have less of the late-stage disease. But they have about the same proportion of the late-stage disease, and they have a much higher mortality rate, just like their incidence rates,” said Clarke, according to an article on the ABC News web site.

Clarke seems quite convinced that a higher socioeconomic status is a risk factor for breast cancer. Along these lines, she hypothesizes that the climb in Marin’s breast cancer rates in the 1990s may be linked to the departure of low-income women who could no longer afford to live there, a process responsible for Marin’s status as one of the nation’s smallest urban counties. Clarke hopes that this “petri dish” phenomenon will enable researchers to study what it is about the life of a professional, well-off white woman in Marin County that apparently makes her susceptible to breast cancer.

“I just can’t help but wonder if this is, you know, the canary in the coal mine,” says Clarke. “And this could be happening in smaller [affluent] communities that are, you know, swallowed up in big counties and we’ll never be able to do good cancer surveillance on a yearly basis there ... the way we can in Marin.”

A recent study carried out in Newton, Massachusetts by the Silent Spring Institute and funded by the state Department of Public Health studied differences between women living in areas of high and low breast cancer incidence. In a press release the institute noted, “Breast cancer researchers have long known that higher socioeconomic status is associated with higher breast cancer risk. But what has remained a mystery is unraveling what about higher socioeconomic status leads to the increased risk.”

The researchers found in the higher-incidence areas “more routine pesticide use ... and ... a parallel pattern of more routine pesticide use in homes with higher income or education.” They noted that the pesticide finding is “intriguing because components of many pesticides contain endocrine disrupting compounds” which may increase the risk of cancer.

“We know that lifetime exposure to estrogen is a risk factor,” Tufts University professor Sheldon Krimsky, who studies environmental health hazards, commented to a Washington Post reporter. “So it is logical that if we have chemicals that are creating more estrogen, the risk may go up.” According to Krimsky, these chemicals exist in cosmetics, lawn care products, household cleansers and certain plastics, but he complained that research into the potentially harmful effects of these chemicals is proceeding “at a snail’s pace.”

It should be noted that the Newton study, contrary to Clarke’s assertion that higher-quality medical care is a non-factor, goes on to caution that “women in the high incidence area reported higher breast cancer screening rates. Because screening leads to earlier diagnoses, it may contribute to higher reported incidence without indicating a higher incidence of disease.”

Some women in Marin County have expressed frustration with the exclusive focus on demographics.

“It’s easy for them to say ‘demographics,’ but—hello? There hasn’t been enough research yet into what’s in our air and in our soil and in the products we use,” Fern Orenstein, a health education specialist and cancer survivor, told the Reuters news agency. “Maybe what it is isn’t unique to Marin, but it is environmental, and we just have more of it here.”

Overall breast cancer trends

Whether breast cancer is more likely to strike upper middle class professional women or whether the Marin statistics are to be explained by an environmental problem specific to the county or a combination of factors, it is certain that socioeconomic status is linked to the rates at which cancer victims survive the disease.

The 2001-02 report by the American Cancer Society outlines statistically that lack of health insurance and poverty, particularly among black women, are the biggest factors determining breast cancer survival.

A national study published in the October 1 issue of the journal Cancer concluded that older black Medicare breast cancer patients “may receive less aggressive treatment for their breast carcinomas than whites.” Mortality rates among black women have risen as overall breast cancer mortality rates have declined. The report is only one of a few that focused on a large group of black women.

The researchers noted that black women were 36 percent more likely to have their entire breasts removed to treat the cancer, versus breast-conserving surgery, and 50 percent less likely to receive radiation therapy. Lead author Dr. Jeanne Mandelblatt, director of the cancer control program at the Georgetown University Medical Center, stated that while breast conservation surgery and mastectomy have equal survival rates, “omission of radiation can lead to higher local recurrences and more treatment.”

The study found that the distance a black woman lived from a cancer center, the poverty of her neighborhood and the patient’s other illnesses affected whether or not she obtained radiation treatment. Conversely, these factors did not play a role in a white woman’s likelihood of receiving radiation treatment, according to the researchers.

Mandelblatt said that the study focused on Medicare fee-for-service patients, rather than those belonging to the more restrictive, but increasingly more common, Medicare managed care program. She concluded, among other things, that universal health insurance might equalize access to care.

Breast cancer rates across the country have dramatically increased in recent years. A woman’s lifetime risk of contracting the disease now stands at 1-in-8 in the US (Marin County’s risk factor is 1-7). This is three times the 1-in-22 rate of just 50 years ago. According to the Centers for Disease Control and Prevention, it is estimated that 200,000 women will be diagnosed with breast cancer and 40,000 will die of the disease this year alone.

Commenting on the Marin County crisis, Dr. Ana Soto of Tufts Medical School told Reuters: “I believe it is high time to seriously consider environmental chemicals as the most likely cause of this sudden increase in risk.” Soto said that while many breast cancer studies focus on genetics, or on “lifestyle” factors such as reproductive history, alcohol use and exercise, little research is being conducted to assess how environmental toxins may be causing cancer. “The increasing risk of breast cancer and other cancers has paralleled the proliferation of synthetic chemicals since World War II,” said Soto, adding that only 7 percent of the estimated 85,000 synthetic chemicals registered for use in the United States have been subjected to toxicological screening.