Crude incidence rates of breast cancer among U.S. female active component service members have fluctuated slightly over the past 12 years, but have remained relatively stable, according to a new study.
As in the general U.S. population, with the exception of skin cancer, breast cancer is the most frequent cancer diagnosis among women. During the 13-year surveillance period from 2000 to 2012, 1,092 female active component members were diagnosed with breast cancer, according to the study published in the Medical Surveillance Monthly Report, a peer-reviewed journal on illnesses and diseases affecting service members from the Armed Forces Health Surveillance Center (AFHSC). Of those diagnoses, 244 (22.3 percent) of were ductal cinoma in situ (DCIS) cases. The overall crude incidence rate of breast cancer was 40.6 per 100,000 person-years (p-yrs); the lowest annual incidence rate was 28.6 per 100,000 p-yrs in 2006, and the highest annual incidence rate was 53.6 per 100,000 p-yrs in 2001.
"The most important observations from this study of active component service women were annual incidence rates of breast cancer have fluctuated up and down from year to year during the last 13 years but there has been no discernible long-term trend upward or downward," said Army Colonel William Corr, the deputy director of AFHSC's division of Epidemiology and Analysis. "In addition, approximately 22% of all breast cancers diagnosed during the period were ductal carcinoma in situ (DCIS), the least invasive form of breast cancer."
This report provides new estimates of breast cancer rates and expands upon previous analysis by providing incidence rates for DCIS. The surveillance period was January 1, 2000 to December 31, 2012. The surveillance population included all women who served in the active component of the U.S. Armed Forces at any time during the surveillance period. All data used to determine incident cancer cases were derived from records routinely maintained in the Defense Medical Surveillance System (DMSS) maintained by AFHSC.
Over the surveillance period, the crude incidence rate of DCIS cases was 9.1 per 100,000 p-yrs; for other (invasive) breast cancer diagnoses the rate was 31.5 per 100,000 p-yrs. While crude incidence rates of invasive breast cancer fluctuated during the period, the crude incidence rate in the final year of the surveillance period was slightly lower than the rate in the first year of the surveillance period (2012: 32.1 cases per 100,000 p-yrs; 2000: 33.8 cases per 100,000 p-yrs)
In contrast, crude incidence rates of DCIS fluctuated less dramatically during the period, but incidence rates were higher in 2012 than in the first year of the surveillance period (2012: 11.0 cases per 100,000 p-yrs; 2000: 8.0 cases per 100,000 p-yrs). While DCIS is less common than invasive breast cancer, the widespread adoption of breast cancer screening (i.e., mammography) has led to marked increases in DCIS diagnoses as most cases of DCIS are diagnosed through mammography screening.5
The strongest demographic correlate of increased risk of a breast cancer diagnosis was older age For example, the highest rates of diagnoses were among those older than 40 years. Incident cases of DCIS were relatively uncommon in female military members under 40 years of age; crude incidence rates were sharply higher in those 40 years of age or older compared to those 35-39 years of age (79.0 per 100, 000 p-yrs and 16.5 per 100,000 p-yrs, respectively).
Similar age-related increases in crude incidence rates were observed for invasive breast cancer. Crude incidence rates of both DCIS and invasive breast cancer were lower among members of the Marine Corps than the other Services (Table 1). Military members in health care occupations were much more likely than members of other occupation groups to be an incident breast cancer case (IRR: 2.1).
Black, non-Hispanic women had higher overall crude incidence rates of breast cancer (rate: 49.0 per 100,000 p-yrs) than women in any other race-ethnicity category. This finding was true for both cases of DCIS and invasive breast cancer.
In the U.S. civilian population, the average annual breast cancer rate is highest in white, non-Hispanic women, followed by black, non-Hispanic (African American) women. In contrast, this analysis of active component military women found that black, non-Hispanic women had the highest crude incidence rates of breast cancer (both invasive and DCIS). One factor that may contribute to this difference is the prevalence of screening mammography by race/ethnicity among female military members.
Active military populations differ from the U.S. civilian population in many ways. Several risk factors that differ in the populations affect the incidence of breast cancer. Because women in the military are subject to relatively intensive medical screening, cancers may be detected earlier in their clinical courses in active military than in civilian populations. If so, rates of cancer diagnoses may be higher among active military members than similarly aged civilians (because cases are detected earlier); however, the detection and treatment of cancers at earlier stages may decrease cancer-related mortality among military members compared to civilians.
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