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Mammograms detect
ductal carcinoma in situ (DCIS), is that a good
thing? |
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 Nearly all breast cancer
arises in the milk ducts of the breast. When
cancer cells grow and spread outside these ducts
the cancer is considered to be invasive (upper
figure). DCIS is a breast
lesion that is contained within the milk ducts of
the breast (lower figure). DCIS lesions contain
cells that appear to be cancer but not all such
lesions behave as cancer, i.e. they will not spread
outside the ducts and invade surrounding tissue
nor will they be life-threatening. In other words,
only some DCIS lesions will eventually become invasive
cancer. What percent will become invasive
cancer is not known. Almost all women
who have DCIS detected are currently treated by
surgery, either a mastectomy (removal of the
breast) or a lumpectomy (excision of the tumor)
with or without radiation. Based on current knowledge,
doctors cannot tell which DCIS lesions will become
invasive cancer and which will not. Detecting DCIS
on mammograms may benefit those women whose DCIS would
become invasive cancer. However, it may potentially harm
those women who have breast surgery but whose DCIS would
never become invasive cancer.
One large study of women aged 50-59 years found that women who underwent
routine mammograms and clinical breast examinations were 4 times
more likely to have detection of DCIS as women who only had routine
clinical breast examinations. Yet, the same number of breast cancer
deaths were prevented among women who underwent routine mammograms and
clinical breast examinations as women who only had routine clinical
breast examinations. Thus, the value of detecting DCIS lesions on
mammograms is not clear.
If 10,000 40 year
old women get routine mammograms over the next 10
years, 40 to 50 will turn out to have DCIS.
If 10,000 50 year
old women get routine mammograms over the next 10
years, 70 to 120 will turn out to have DCIS.
If 10,000 60 year
old women get routine mammograms over the next 10
years, 110 to 120 will turn out to have DCIS.
If 10,000 70 year old women get routine
mammograms over the next 10 years, 95 to 150 will turn out
to have DCIS.
The chance that any women 40 or older diagnosed
with DCIS who receives treatment will die of invasive breast
cancer in the next ten years is about 2% (about 2 of every
100 women).
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References:
Ernster VL, Barclay J,
Kerlikowske K, Grady D, Henderson IC. Incidence of and
treatment for ductal carcinoma in situ of the breast.
JAMA 1996;275:913-918.
Kerlikowske K, Barclay J. Outcomes of modern screening
mammography. Monogr Natl Cancer Inst 1997;22:105-111
Ernster VL, Barclay J, Kerlikowske K, Wilkie H, Ballard-Barbash R.
Mortality among women with ductal carcinoma in situ of the breast
cancer in the population-based SEER Program. Arch Intern Med 2000;160:953-958.
May DS, Lee NC, Nadel MR, Henson RM, Miller DS. The National Breast
and Cervical Cancer Early Detection Program: report on the first 4
years of mammography provided to medically underserved women. Am J
Roentgenol. 1998;170:97-104
Kerlikowske KM, Grady DG, Barclay J, Sickles EA, Eaton A, Ernster V. Positive
predictive value of screening mammography by age and family history of breast
cancer. JAMA 1993; 270:2444-50.
Miller AB, To T, Baines CJ, Wall C. Canadian National Breast Screening
Study-2: 13-year results of randomized trial in women aged 50-59 years.
JNCI 2000;92:1490-9.
Image adapted from Breast Health with permission of the
publisher ©(1994) Business and Legal Reports, Inc., 39
Academy Street, Madison, CT, 06443.
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