Monday 20th February 2017


Breast Cancer AwarenessOn this page go to:

What is DCIS

DCIS stands for Ductal Carcinoma In Situ (sometimes called intraductal carcinoma), an early form of breast cancer or pre-cancer which has not spread (in situ is Latin for 'in the original place'), so it is non-invasive. This condition is distinguished from Invasive Ductal Carcinoma (IDC), in which breast malignant cells proliferate.

DCIS is called "ductal" because it is limited to the breast's milk ducts (or lactiferous ducts, where most breast cancers originate) and has not spread to the surrounding breast tissue or any other part of the body. The word "carcinoma" is the medical term for most human cancers.

Ductal Carcinoma In Situ is a Stage Zero cancer, a contained tumour that has not spread; some scientists consider it the earliest form of cancer, but others think that it should not even be called "cancer" because it is a misleading label, confusing both doctors and patients.

The problem with a DCIS diagnosis is that it carries an uncertain prognosis: it may spread and become life-threatening or it may never do that, and there is no way to predict its natural course.

DCIS statistics can give an indication of its clinical history: it is believed that between 1 and 5 out of 10 cases of DCIS will eventually become invasive cancer within 20-30 years.

The other cases of DCIS never progress at all and would never have been seen or felt in any way during the woman's lifetime if not for the mammogram, and would have never created any problem.

When Ductal Carcinoma In Situ is detected, the diagnosed individual is normally treated, to be on the safe side.

So the women whose DCIS would not have advanced suffer all the physical and psychological consequences of living with a diagnosis of invasive breast cancer which they may not have, like the rigours of breast cancer treatment and the anguish associated with such a diagnosis.

Since DCIS almost never causes symptoms or a lump that can be felt, it is almost invariably discovered by breast screening mammography.

When younger women undergo breast screening mammography, most of the cancers found are DCIS.

An almost unknown condition before the advent of mass breast screening, DCIS is now common, representing about 20% to 30% of all breast cancers found by mammography - 1 out of 5 in 2010. DCIS was rare before the start of the wide use of mammograms in the 1980s; the increase in its incidence since 1980 has been an astronomical 600 percent. Better diagnosis or over diagnosis? That is the question.


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DCIS and Mammogram

Efforts to make a diagnosis of breast cancer at an ever earlier stage have created previously non-existent problems. Interestingly, basic scientists have uncovered biologic mechanisms that stop the progression of cancer. All this means that early diagnosis of breast cancer, which had so far been considered a breakthrough, could in fact include in worringly large measure detections of breast abnormalities that conform to the pathologic definition of cancer but are in reality harmless.

Not much is yet known about DCIS and its course, but we know that, although half or more of all the cases will not progress to be invasive, these women will still be treated with radiotherapy, drugs and surgery.

Several studies have found that the likelihood of being overdiagnosed after mammography is not very small: it is indeed 10 times greater than the likehood of avoiding death from breast cancer. A study in the British Medical Journal analyzing benefits and harms of screening for breast cancer says:

"If 2000 women are screened regularly for 10 years:
  • 1 woman will avoid dying from breast cancer
  • 10 healthy women, who would not have been diagnosed without screening, will have breast cancer diagnosed and be treated unnecessarily; 4 of these will have a breast removed, 6 will receive breast conserving surgery, and most will receive radiotherapy."

An article in the Journal of the National Cancer Institute says of the two risks of progression - of the same lesion and elsewhere - associated with DCIS:

"Although no one is sure what the probability of progression is, studies of DCIS that were missed at biopsy (1,2) and the autopsy reservoir (3) suggest that the lifetime risk of progression must be considerably less than 50%. ...Again, although no one is sure what this probability is, a recent prospective study of a cohort of patients with DCIS who were treated largely by excision alone suggested that the 5-year risk of subsequent invasive breast cancer elsewhere is less than 10% (4)." [Emphasis added]

The article adds that generally women diagnosed with DCIS are understandably anxious because they perceive their chances of developing invasive cancer as much higher than they actually are. And all this because of mass mammography, of which the anxiety must be considered a deleterious consequence. But not the only one, as the above article continues:

"The fundamental paradox of early cancer detection is that, while some may be helped, others get a diagnosis they'd be better off without. The central harm of screening is overdiagnosis—the detection of abnormalities that meet the pathologic definition of cancer but will never progress to cause symptoms. Although this concept may seem implausible to clinicians, basic scientists have begun to uncover biologic mechanisms that halt the progression of cancer (6–8). Overdiagnosis has now been associated with early detection in a variety of cancers... Although it is impossible to determine which individuals are overdiagnosed (unless they are not treated and ultimately die without ever developing symptoms from their cancer), it is possible to identify subsets of patients who are at high risk of overdiagnosis. In breast cancer, this subset is patients with DCIS. Because the "best guess" is that most DCIS won't progress to invasive cancer, the risk of overdiagnosis would be expected to be greater than 50%. The problem with overdiagnosis is that it leads to overtreatment."

Not just in situ, non-invasive cancers regress spontaneously. An important research in The Lancet has found that even many screen-detected invasive breast cancers would regress spontaneously if not discovered during mammography screening.


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Overdiagnosis to some extent is the rule rather than the exception in cancer screening. Since it is impossible to know which screened persons are overdiagnosed, almost all are treated as if they had invasive malignant cancer. Overdiagnosed individuals do not benefit from treatment because they would have had no symptoms and would not have been affected in any way by their "disease", to the point of not even noticing it.

To these individuals treatment can only cause harm, in the form of side effects of chemotherapy, damage from radiotherapy, and invasive, disfiguring surgery. Today, practically every woman diagnosed with Ductal Carcinoma In Situ undergoes lumpectomy (removal of part of a breast) or mastectomy (removal of a whole breast) and most will receive radiation: a treatment pattern that is extremely close to that of early-stage invasive breast cancer.

A study by the University of California's Department of Epidemiology and Biostatistics, School of Medicine, published in the Journal of the National Cancer Institute found:

"The increased use of screening mammography has resulted in a marked increase in detected cases of ductal carcinoma in situ (DCIS) of the breast since the early 1980s. In 1993, there were an estimated 23,275 newly diagnosed cases of DCIS in the United States, of which 4,676 were in women aged 40-49. DCIS accounted for 14.7% of all newly diagnosed breast cancers in women aged 40-49 in 1993, and perhaps 40% of all mammographically detected breast cancers in this age group are DCIS. Among women aged 40-49, an estimated 1,890 mastectomies and 2,707 lumpectomies (with or without radiation) were performed for DCIS in 1993. There is an urgent need to better understand the relationship of mammographically detected DCIS to invasive and potentially life-threatening breast cancer. Better information about the appropriate treatment of DCIS is also needed to reduce the confusion and uncertainty many women and their physicians currently experience in the face of a DCIS diagnosis. For the present, women considering screening mammography should be told the likelihood of being diagnosed with DCIS and that only some DCIS cases may be clinically significant but almost all will be treated surgically." [Emphasis added]

A study published in Archives of Internal Medicine on the "Likelihood That a Woman With Screen-Detected Breast Cancer Has Had Her 'Life Saved' by That Screening" concludes:

"Today, more people are likely to know a cancer survivor than ever before. Between 1971 and 2007, the number of cancer survivors in the United States more than doubled, from 1.5% to 4.0% of the population. Breast cancer survivors are particularly common: they now represent approximately 2.5 million, or one-fifth of the current survivor population. Earlier diagnosis (either via enhanced awareness or screening) and better treatment are clearly part of the explanation for this large survivor population. But so too is the enthusiasm for screening and the resulting overdiagnosis. And, ironically, this enthusiasm may, in turn, be the product of a large number of survivors. This self-reinforcing cycle (the more detection, the more enthusiasm—the so-called popularity paradox of screening) is driven, in part, by the presumption that every screen-detected breast cancer survivor has had her 'life saved' because of screening. Our analyses suggest this is an exaggeration. In fact, a woman with screen-detected cancer is considerably more likely not to have benefited from screening. We believe that this information is important to put cancer survivor stories in their proper context." [Emphasis added]


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Photo accompanying the article Love Them by Caitlinator made available under an Attribution 2.0 Generic (CC BY 2.0).