Early detection of breast cancer by mammography allows women to access more favorable treatment options and has resulted in an overall reduction in mortality of approximately 20 percent to 40 percent and improved survival.1 In 2009, the U.S. Preventive Services Task Force (USPSTF) changed breast cancer screening guidelines for mammograms from every one year to two years in women ages 40 or older to biennial.2,3 The change affected women ages 40 to 50 more than other age groups, but trends in prevalence of screening for these women appear to vary based on ethnicity and insurance coverage.4
To explore the potential impact of changes in screening prevalence, we explored data on metastatic breast cancer (MBC) before and after the guidelines changed. Some research has suggested that the incidence of MBC at the time of initial diagnosis is rising among women younger than age 45.1 A National Cancer Database (NCDB) analysis showed the change in screening guidelines resulted in a slight increased trend overall of MBC cases among women 40−50 years old at diagnosis in Commission on Cancer (CoC)-accredited programs. Increases in MBC varied based on insurance status and race/ethnicity. Further data on screening prevalence and diagnosis of MBC for women in this age group by race and insurance coverage are needed.
Breast cancer and screening
Early detection of breast cancer by screening mammography allows women to undergo more favorable treatment options and has a demonstrably positive effect on overall mortality and survival rates.5
In November 2009, the USPSTF changed breast cancer screening guidelines for mammograms from every one to two years in women 40 years old or older to biennial (that is, every other year) in women ages 50–74 years old.2,3 The guidelines were revised to prevent assumed overtreatment for low-risk early cancers, unnecessary biopsies, and false positives and mostly affected women between 40–50 years old.6
Early detection of breast cancer by screening mammography allows women to undergo more favorable treatment options and has a demonstrably positive effect on overall mortality and survival rates.
Subsequently, other national organizations put forth screening guidelines that differed, resulting in a variety of approaches available to clinicians and their patients. Ultimately, decisions regarding screening behaviors have been left to the individual patients and their clinicians to develop personalized screening guidelines.
It has been reported that annual mammogram rates significantly decreased after the guideline change. Data from the National Health Interview Survey (NHIS) from 2015 show a declining trend from 2008 to 2015 in women ages 40−49. But trends in prevalence of screening appear to vary based on ethnicity and insurance in this age group.7,8
Exploring impact of screening
A lower prevalence of screening may affect rates of stage at diagnosis. A study that performed a cross-sectional trend analysis using data from U.S. Cancer Statistics (USCS), National Program for Cancer Registries (NPCR); and the Surveillance, Epidemiology, and End Results (SEER) Program showed that the average annual incidence of ductal carcinoma in situ (DCIS) and MBC increased slightly in women ages 40–49 compared with the years prior to 2009.4
Approximately 5–9 percent of newly diagnosed breast cancer patients have MBC (Stage IV). While the survival rates in MBC have improved, overall survival is only 27 percent.5
To understand the potential impact of changes in screening prevalence, we investigated MBC with specific attention to patients between the ages of 40–50 years old. We used the NCDB to explore trends in MBC (before and after the screening guideline changes).
NCDB analysis of MBC diagnosis
The NCDB was used to examine MBC cases from diagnosis years 2008 to 2017. Breast cancer was defined as any case with a primary site of C50.0–C50.9 and has any histology not in 9050–9055, 9140, and 9590–9992. MBC was characterized as any breast cancer that either had a clinical M of cM0(I+), M1, cM1, cM1a, cM1b, cM1c, pM1, pM1a, pM1b or pM1c, or clinical stage group of IV, IVA, or IVB. Any case with age at diagnosis of younger than 40 years old or older than 50 years old was excluded; only females were studied.
For this analysis, insurance status was defined as: private insurance; no insurance/Medicaid (including not-insured self-pay); Medicare; or other/unknown. Race and ethnicity were categorized as: Hispanic, non-Hispanic Asian, Hawaiian, Pacific Islander not otherwise specified (NOS), non-Hispanic black, non-Hispanic white, or other/unknown. Analysis included chi-square tests—test for equal proportions and Pearson chi-square statistic—and 95 percent confidence limits at a statistical significance threshold of 0.05.
From 2008 through 2017, 14,364 cases were diagnosed with MBC at ages 40 to 50 years old. In that same time period, the proportion of cases in the NCDB diagnosed with MBC increased to 9.4 percent (1,346 cases) in 2017 from 9.2 percent (1,325 cases) in 2008. The proportion of cases across diagnosis years was not statistically significant (p = 0.0668) (see Figure 1).
To better understand the trend of MBC, further evaluation was performed to describe the proportions based on insurance status and race and ethnicity. We found an association between diagnosis year and insurance status (p = 0.0168). Both Medicare and privately insured patients had a non-significant increase in the proportion of patients with MBC in women age 40–50 between 2008 and 2017; private insurance saw the greatest difference—2.6 percent (see Table 1).
An association between diagnosis year and race and ethnicity (p < 0.0001) also was evident. Patients who were Hispanic, non-Hispanic Asian, Hawaiian, Pacific Islander NOS, or non-Hispanic white saw a nonsignificant increase in proportions of patients among diagnosis years; non-Hispanic black patients experienced a nonsignificant decrease. Also, of the known races or ethnicities, non-Hispanic Asian, Hawaiian, Pacific Islander NOS patients saw the largest differences between 2008 and 2017 at 2.5 percent (see Table 2).
Further investigation needed
Our NCDB analysis showed that, after the change in screening guidelines, the overall proportions of MBC cases among patients 40–50 years old at diagnosis in CoC-accredited programs trended upward only slightly. Within this age group, there was an increase in MBC, based on insurance status and race/ethnicity after the institution of guideline changes. The MBC trend increased among Hispanics, Asians, non-Hispanic whites, and Medicare and privately insured patients. Although changes in screening guidelines cannot be directly linked to the differences elucidated in the NCDB data, they may be the result of multiple factors, including individual barriers, structural barriers, and changes in health policy. Of note, during this time frame, national health policy changes were made related to insurance, including the passage and subsequent weakening of the Affordable Care Act. Certainly, uptake of screening guidelines by providers could impact populations differently.9 Further exploration of factors regarding access to care, such as insurance coverage and uptake to screening in these particular groups, warrant further investigation to better understand these disparities.
Statistical support for this column was provided by Amanda E. Browner, MS, Statistician, NCDB.
The NCDB is hospital-based data. The data comes from CoC-accredited programs. Over time, programs may join or leave accreditation, thus affecting the number of cases over time.
- Marmot MG, Altman DG, Cameron DA, Dewar JA, Thompson SG, Wilcox M. The benefits and harms of breast cancer screening: An independent review. Br J Cancer. 2013;108(11):2205-2240.
- Esserman L, Shieh Y, Thompson I. Rethinking screening for breast cancer and prostate cancer. JAMA. 2009;302(15):1685-1692.
- U. S. Preventive Services Task Force. Screening for breast cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2009;151(10):716-726.
- Guo F, Kuo Y, Berenson AB. Breast cancer incidence by stage before and after change in screening guidelines. Am J Prev Med. 2019;56(1):100-108.
- American Cancer Society. Breast cancer facts & figures 2019–2020. 2019. Available at: www.cancer. org/content/dam/cancer-org/research/cancer-facts-and-statistics/breast-cancer-facts-and-figures/breast-cancer-facts-and-figures-2019-2020.pdf.
- Oeffinger KC, Fontham ET, Etzioni R, et al. Breast Cancer Screening for Women at Average Risk: 2015 Guideline Update from the American Cancer Society. JAMA. 2015;314(15):1599-1614.
- Narayan AK, Mercaldo SF, Gupta YP, Warner ET, Lehman CD, Miles RC. Potential of using mammography screening appointments to identify high-risk women: Cross sectional survey results from the national health interview survey. Breast Cancer Res Treat. November 12, 2020 [Epub ahead of print].
- Shoemaker ML, White MC, Wu M, Weir HK, Romieu I. Differences in breast cancer incidence among young women aged 20–49 years by stage and tumor characteristics, age, race, and ethnicity, 2004–2013. Breast Cancer Res Treat. 2018;169(3):595-606.
- Spring LM, Marshall MR, Warner ET. Mammography decision making: Trends and predictors of provider communication in the Health Information National Trends Survey, 2011 to 2014. Cancer. 2017;123(3):401- 409.