Ductal carcinoma in situ, or DCIS. It’s an ominous-sounding term that’s at the centre of increasing debate over the value of breast screening for middle-aged women.
DCIS is also often referred to as stage-zero breast cancer.
Before preventive mammography screening took hold in the 1980s, these little embryonic cancer cells were unheard of. It’s only with improvements in radiation that they became evident.
In his book “The Big Squeeze: A Social and Political History of the Controversial Mammogram,” Atlanta radiologist Handel Reynolds describes DCIS this way:
“In DCIS, the cancer cells are confined to the
interior of the milk ducts (the cells’ ‘in situ’ or ‘original’ location). Typically there is no lump or other noticeable symptom, and as long as the tumour remains confined to the milk ducts, it cannot spread beyond the breast. DCIS has a 10-year survival rate of 98 per cent.”
One would think the detection of such embryonic cancer cells is a good thing. But an increasing number of specialists, including Reynolds, say it isn’t.
Most aggressive cancers do go through the DCIS stage, but up to 50 per cent of DCIS cases never amount to anything.
“The trouble is, we have no reliable way to separate harmless DCIS cases from potentially dangerous ones,” wrote Reynolds. “As a result, all women who get the diagnosis undergo cancer therapy. Although women with harmless DCIS cannot benefit from treatment, they are still subject to its potential risks.”
This is what’s known as over-diagnosis. And it plays a big part in the mounting evidence that for women under 50, regular screening does little or nothing to decrease the risks involved in breast
This is not a popular message. Screening advocates are loudly dismissive of such arguments. It’s hard to let go of the idea that even one potentially fatal tumour caught at a routine screening is worth the effort.
In 2011, the Canadian Task Force on Preventive Health Care raised eyebrows when it recommended that women age 40-49 should not have regular mammograms. Their finding directly contradicted the direction many provinces were heading in.
In fact, the following March, Newfoundland and Labrador expanded routine testing for women in their 40s, on the condition they provide a referral from their doctor.
This week, research by the Canadian National Breast Screening Study again threw cold water on the effectiveness of screening. The findings are guaranteed to further polarize the debate.
The Globe and Mail’s veteran health reporter André Picard recommends a balanced approach.
“Women should continue to be screened — because the jury is still out on the benefits — but do so every few years without stressing about it,” Picard wrote Wednesday. “They should also be as aware of the possible harms as the potential benefits.”
There are more important things to obsess over, Picard wrote, adding that breast cancer will kill about 5,000 women (and 60 men) this year, representing about four per cent of all women’s deaths.
“Fear should not hang over women like a dark cloud.”