Still, an estimated 370,200 eligible women were not screened within a year of the 2010 survey, said Nicole Dreisbach, a PHMC research associate.
"Certainly, we'd like to see that at 100 percent," she said. "They may not know there are low-cost or free options for getting a screening mammogram."
The survey of 10,000 households in Southeastern Pennsylvania also found that screening rates were much lower among women with lower incomes, less education, no health insurance, or no regular source of health care.
The regional trends mirror state and national patterns. Screening mammography in the United States rose steadily until peaking at 70 percent of eligible women in 2000; since then, it has fallen to about 65 percent, according to the U.S. Centers for Disease Control and Prevention.
Mammography enables early detection of breast cancer, before a lump can be felt.
While that is intuitively a good thing, many experts argue that the decision to undergo regular screening is a close call because mammography doesn't save many lives, even among women age 50 to 69, who are at higher risk than women in their 40s. A 2011 expert review found that mammography screening resulted in a 15 percent decrease in breast cancer deaths. (Put another way, screening 2,000 women every two years for a decade would prevent one death.)
For women in their 40s, the "mortality benefit," if any, is even tinier, while the chance of a false alarm - which would trigger more X-rays, an ultrasound, and maybe a biopsy - is 50-50 over a decade. Younger women tend to have dense breast tissue, which hampers mammography.
"The test is surely a close call, a delicate balance between modest benefit and modest harm," believes H. Gilbert Welch, a Dartmouth Medical School physician who has written books on overdiagnosis and overtreatment.
This debate - much like the one over the benefits of prostate cancer screening with the PSA test - has led to differing guidelines for mammography.
The PHMC subscribes to the recommendation of the American Cancer Society and the American College of Obstetricians and Gynecologists that women 40 and older get a mammogram annually. The National Cancer Institute recommends screening "every one to two years."
But in 2009, the U.S. Preventive Services Task Force, an expert federal panel, advised women age 50 to 75 to get screened every two years. Before 50, the panel said, it "should be an individual" decision.
The panel also said that research is insufficient to assess the value of an annual clinical breast exam performed by a physician.
The American Cancer Society, in contrast, suggests that women in their 20s and 30s have a clinical breast exam as part of an annual gynecological exam.
In Southeastern Pennsylvania, about two-thirds of women age 18 or older, or 478,000 women, had clinical breast exams within the previous year, the PHMC's 2010 survey found.
The PHMC also analyzed 2010 data from women who had never had mammograms. Like national surveys, the regional one found that socioeconomic and racial factors are key.
Only 3.4 percent of women with graduate degrees were never screened, compared with 5.6 with college degrees, 7.1 percent with high school diplomas, and 8.1 percent with less than a high school diploma.
7.8 percent of African American were never screened, compared with 7.1 percent of Latina women, and 5.7 percent of white women.
18.3 of uninsured women were never screened, compared with 7.7 percent of those with insurance.
11 percent of women living far below the poverty line were never screened, compared with 5.2 percent living at or above the line.
Contact Marie McCullough at 215-854-2720 or firstname.lastname@example.org