Study: Descent in breast cancer rate bottoms out
On the heels of the 2002 publication by the Women’s Health Initiative (WHI) revealing the increased risk of breast cancer and other adverse health effects resulting from the use of postmenopausal hormone therapy, use of the therapy tapered and breast cancer incidence among white women in the U.S. plunged by 7 percent between 2002 and 2003, explained Carol DeSantis, MPH, an epidemiologist with the surveillance and health policy department at the American Cancer Society in Atlanta, and co-authors.
DeSantis and colleagues used the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) 12 registries representing 14 percent of the U.S. population to estimate cancer incidence among women in the U.S. The authors assessed trends based on race, age, estrogen receptor (ER) status (ER+ or ER-) and postmenopausal hormone therapy use.
Overall incidence for all groups and variables remained steady between 2003 and 2007, with rates of approximately 138 per 100,000 in whites, 125 per 100,000 in blacks and 87 per 100,000 in Latinos.
However, among all white women ages 60 to 69, breast cancer incidence increased by 4.8 percent between 2006 and 2007, while white ER+ women ages 40 to 49 experienced a 2.7 percent yearly increase in cancer incidence between 2003 and 2007.
In contrast, breast cancer rates among white ER- women decreased for all age groups. ER+ women accounted for the majority of breast cancers.
ER+ cancer rates between 2003 and 2007 also increased among black women, by 5.2 percent per year for those ages 40 to 49; between 2005 and 2007 rates also increased significantly for blacks between the age of 50 and 69.
Latino women showed the lowest rates of breast cancer, presenting with insignificant increases between 2003 and 2005 and modest decreases from 2005 to 2007.
“Overall breast cancer incidence rates among NH [non-Hispanic] white women did not continue to decrease after 2003,” the authors noted. Prior to 2003, whites experienced the largest drop in cancer rates, with those of blacks and Latinos remaining relatively steady.
The authors noted that their findings confirmed several non-population based U.S. and Canadian studies showing similar stabilization of rates. On the other hand, a recent study estimated that breast cancer incidence would experience wide-ranging drops across the EU (to learn more, click here).
The stabilization of rates occurred despite continued, albeit less intense, decreases in hormone therapy (estrogen and progestin) use among all groups. The authors hypothesized that, in addition to the slowing reductions in hormone therapy, steady mammography screening rates and increased sensitivity resulting from less hormone therapy probably contributed to the leveling off of breast cancer.
“It is not clear why ER+ and ER- breast cancer rates among black women may have increased for certain age groups. One hypothesis is that recent breast cancer incidence trends in black women reflect trends in the prevalence of obesity, which increased through the mid-2000s,” the authors noted.
“Also, reasons for the higher rates of ER- breast cancer in black women compared to white and Hispanic women are not fully understood, but are thought to reflect a complex interaction of genetic, environmental and behavioral factors.”
The authors concluded by saying that “[f]urther studies are needed to better understand the recent breast cancer trends.”