Next time someone asks you what exactly public health does, repeat this number: 4.3 million. That’s the number of women — mothers, sisters, wives, aunts, grandmothers, daughters and friends — who might have otherwise gone without timely breast and cervical cancer screenings if it weren’t for public health and its commitment to prevention.

This year marks the 23^rd anniversary of the National Breast and Cervical Cancer Early Detection Program, which the Centers for Disease Control and Prevention launched in 1991 to ensure that low-income women would have the same opportunity to detect cancers in their earliest stages and when treatment is often easier and more effective. The program and its success are the subject of the most recent supplement of Cancer, a journal of the American Cancer Society, and represents the first time such detailed information about the program’s success and strategies has been published. According to the published research, more than 4.3 million women with limited access to health care received breast and cervical cancer screening and diagnostic services in the first 20 years of the CDC program, which provided more than 10.7 million screening examinations. The number of women screened has grown from 82,000 in the early years to more than 500,000 every year.

Also in the program’s first two decades, program providers detected 56,662 breast cancers, 3,206 cervical cancers and 152,470 precancerous cervical lesions. More than 90 percent of women in whom cancer or lesions were detected received appropriate and timely follow-up care. In 2012 alone, the CDC program screened more than 340,000 women for breast cancer, diagnosing nearly 6,000 cancer cases, and more than 251,600 women for cervical cancer, diagnosing 261 cancer cases and about 12,400 premalignant cervical lesions. And providing these screening and diagnostic services to those who might not otherwise have had access cost just $145 per person.(Unfortunately, funding cuts at both state and federal levels do threaten the program’s reach — learn more about that at the Cancer Action Network.)

In addition to opening access to screening and diagnostic services, the CDC program, which funds health agencies in all 50 states, Washington, D.C., five territories and 11 tribal organizations to implement the program on the ground, also connects women to timely follow-up testing, treatment and case management. The CDC program was designed to address a critical service gap: While research had shown that regular cancer screenings could reduce the risk of dying from cancer, poor and uninsured women were less likely to receive the potentially life-saving services and were often diagnosed with cancer at a later stage in the disease cycle. As such, the CDC program is well positioned to positively impact disparities in cancer. For example, in one of the Cancer journal studies, the authors noted that Hispanic women experience the highest rate of developing cervical cancer, and black women experience a disproportionate rate of breast and cervical cancer mortality.

The National Breast and Cervical Cancer Early Detection Program takes a decisively public health approach to providing this traditionally clinical service, designing localized programs that reach low-income women where they are and reducing social and economic barriers that often impede access. In one of the journal studies, authors Jacqueline Miller, Vivien Hanson, Gale Johnson, Janet Royalty and Lisa Richardson write about the Wisconsin Well Woman Program (WWWP), which launched in 1992 with funding from CDC. The Wisconsin program zeroes in on reaching women ages 45 to 64 years old who are underinsured or don’t have any insurance and who are living at or below 250 percent of the poverty level. It also aims to reach Hispanic, black and Native American women as well as women in rural communities. The decentralized state program engages local agencies to tailor education, outreach and enrollment activities that resonate with their residents. The authors write:

The WWWP has developed a network of more than 1,060 provider sites statewide for breast and cervical cancer screening in order to maintain screening services within a 50-mile radius of a woman’s residence. The WWWP provider network includes ambulatory surgery centers, family planning clinics, federally qualified health centers, hospitals, independent laboratories, mammography facilities, pathologists, radiologists, nurse practitioners, rural health clinics, and tribal health clinics. Covered services are available from participating providers at no cost to WWWP clients.

The WWWP has provided more than 490,000 examinations to more than 70,000 Wisconsin women since the program began providing screening services on June 1, 1994. Program data indicate that over the last 18 years, 74% of the women receiving program mammograms were white, 12% were black, and almost 3% were Native American. Hispanic women accounted for 11% of program mammograms. Over this period, the WWWP has diagnosed 1,023 invasive breast cancers and 94 invasive cervical cancers.

However, the same study notes that many more women need to be reached. The authors write that the CDC program only reaches about 13 percent of women who are eligible for the program’s breast cancer screening and 9 percent of women eligible for cervical cancer screening. Of course, with the implementation of the Affordable Care Act (ACA), access to such screenings is likely to change. Still, in one of the journal studies examining the impact of health reform, authors estimated that even with full implementation of ACA — which assumes all 50 states expand their Medicaid programs — 4.5 million women would still be eligible for cervical cancer screening via the CDC program and 1.7 million would be eligible for breast cancer screening. In reality, only about half of states decided to expand Medicaid eligibility.

That Medicaid gap is just one of the many reasons why there’s still a significant need for a public health approach to cancer screening. As one of the journal studies noted: “Limited health literacy or self-efficacy, language barriers, lack of knowledge about screening, fear of cancer, and geographic isolation are common patient barriers that will not be addressed by improved health insurance coverage alone. …These factors (and others) call for partnerships between public health, communities and the health care system to leverage each other’s expertise, connections, and resources to implement more organized and coordinated efforts to increase use of clinical preventive services, which include cancer screening.”

To learn more about the National Breast and Cervical Cancer Early Detection Program, visit CDC or the Cancer journal. And for a handy infographic on the program’s success, click here.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.