Number of breast cancer and DCIS cases diagnosed per year

What is DCIS?

Ductal carcinoma in situ (DCIS) is a very early stage non-invasive breast cancer. A diagnosis of DCIS indicates that breast carcinoma is present, but has not yet infiltrated the lining of the breast ducts. There are many different types and grades of DCIS, most of which are not life threatening. Prior to 1980, DCIS was rarely diagnosed. But with recent advances in breast cancer screening procedures and increased participation in screening mammography, DCIS now comprises up to 25% of all breast cancer diagnoses in the United States. Overall about 20% of new breast cancer diagnoses are given at the DCIS stage. The good news is that the survival rate when DCIS is diagnosed is close to 98%.

Ductal carcinoma in situ is usually detected through microcalcifications

There are a number of ways to confirm DCIS, but it is mostly identified by the presence of certain patterns of microcalcifications on the mammogram. By contrast, invasive breast cancer is typically identified as a mass or architectural distortion on the mammogram.

Breast cancer tumors at time of first detection tend to be small and 'node negative'.

In Canada, studies have shown that for women aged 50-69, of positive findings, an invasive tumor of less than 1.5 cm is detected about 54% of the time, with a 'node negative' status about 77 % of the time. (Node negative means that the cancer has not spread into the lymph nodes) This means that even if breast carcinoma is not diagnosed at the DCIS stage, the odds of discovering and successfully treating breast cancer at an early invasive stage are still very good.

The relative rates of DCIS and invasive breast cancer remain about the same over time.

The chart below, sampled between 1996 and 2003 in the USA, demonstrates the relative rates for DCIS as compared to full breast cancer remain about the same over time. It also shows that the total number of breast cancer and DCIS cases in that country tended to hover around 6000 women during that time period. Overall the ratio of DCIS to breast cancer for all age groups appears to be between 15% and 20%.

Number of breast cancer and DCIS cases per year

number os cases of breast cancer per year

 

Breast Cancers and DCIS diagnosed by mammography by age 10 year age group, in the USA.

Initial screening for breast cancer sorted by different age groups underlines the fact that the earlier the screening begins, the rate of DCIS as compared to cancer will increases. In the graph below, one can observe that DCIS is most commonly diagnosed between the ages of 40 and 59, and is very uncommon for women under 30. This gives further support for breast cancer screening beginning at age 40 and continuing through the 50s. Most of the time, DCIS is a much better diagnosis and prognosis, resulting in fewer mortalities. In North America , initial screening procedures typically identify DCIS about 30% of the time for women over 40, as compared to 70% breast cancer diagnosis.

DCIS and invasive breast cancer rate by age group

 

DCIS rates have increased since the 1990s, while invasive breast cancers are in decline.

Invasive breast cancer rates did not increase during the late 1980s and have in fact declined since 2000. However, during this period the rate of DCIS diagnosis has increased by 200%. The use of screening mammography increased by approximately 250% during the same period, although with a peak increase much sooner than the increase of DCIS detection. The graphic below clearly demonstrates both the upward tradjectory of DCIS detection in the late 1980s, coinciding with improved screening procedures, and a peak and subsequent decline in invasive bresat cancer diagnosis since around 1998.

Rates of DCIS and Invasive Breast Cancer 1975 - 2005

breast cancer and dcis rates

 

DCIS is frequently 'over-diagnosed'

Over-diagnosis is a term now frequently associated with DCIS. Over-diagnosis means that the DCIS would not have otherwise been detected during a woman's lifetime without screening. In other words, the DCIS would not have posed any health problem. Between 15% and 18% of DCIS diagnoses are thought to be over-diagnosed. The concern is that a majority of DCIS cases are treated by surgery. In some instances DCIS has been treated by mastectomy when it may be completely unnecessary.

 

References

  1. U.S. National Institutes of Health, Breast Cancer Surveillance Consortium Statistics, 2005.
  2. Bassett L. Breast imaging Update 2003. Montréal, Canada, August 8-10, 2003.
  3. Paquette D, Snider J, Bouchard F, Olivotto H, for the Canadian Breast Cancer Screening Initiative. Performance of screeningmammography in organized programs in Canada in 1996, CMAJ 2000;163(9):1133-8. www cma.ca/cma
  4. Organized Breast Cancer Screening Programs in Canada; 1999-2000 Report.
  5. Ernster VL, Barclay J, Kerlikowske K, et al.: Incidence of and treatment for ductal carcinoma in situ of the breast. JAMA (1996) 275 (12): 913-8,
  6. Trentham-dietz, A., Sprague, BL., Alagoz, O. Reaidi, P., Rosenberg, M., Gangnon, RE., Stout, NK., The Impact of Detection and Treatment of Carcinoma In Situ on Breast Cancer Mortality.,Cancer Epidemiol Biomarkers Prev (April 2011) 20; 720
  7. Diagnosis and Management of Ductal Carcinoma in Situ (DCIS). Prepared by Minnesota Evidence-based Practice center, Minneapolis, Minnesota., 2010.
  8. Feig SA, Shaber GS, Patchefsky A, et al. Analysis of clinically occult and mammographically occult breast tumors. AJR Am J Roentgenol (Mar. 1977) 128(3):403-8.
  9. Evans WP, 3rd, Starr AL, Bennos ES. Comparison of the relative incidence of impalpable invasive breast carcinoma and ductal carcinoma in situ in cancers detected in patients older and younger than 50 years of age. Radiology(Aug. 1997 ) 204(2):489-91.
  10. Duffy SW, Agbaje O, Tabar L, et al. Overdiagnosis and overtreatment of breast cancer: estimates of overdiagnosis from two trials of mammographic screening for breast cancer. Breast Cancer Res (2005) 7(6):258-65.
  11. Barchielli A, Federico M, De Lisi V, et al. In situ breast cancer: incidence trend and organised screening programmes in Italy. Eur J Cancer (May 2005) 41(7):1045-50.
  12. Schairer C, Mink PJ, Carroll L, et al. Probabilities of death from breast cancer and other causes among female breast cancer patients. J Natl Cancer Inst (Sept. 2004) 96(17):1311-21.
  13. Dawood S, Broglio K, Gonzalez-Angulo AM, et al. Development of new cancers in patients with DCIS: the M.D. Anderson experience. Ann Surg Oncol (Jan 2008)15(1):244-9.

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Copyright Steven B. Halls, MD Last edited 05-July-2011

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