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Patients, Doctors Overrate DCIS Risk

Ductal Carcinoma in Situ: High Anxiety Over Small Risk of Invasive Breast Cancer
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Low-Risk Breast Cancer -- Except When It's Not

DCIS is ductal carcinoma in situ. The "carcinoma" part is truly scary. Just as it sounds, it means cancer. But the "in situ" part is every bit as important. It means that this cancer isn't going anywhere. DCIS is, by definition, confined to the breast ducts. It does not invade the rest of the breast, or the rest of the body.

It's very unusual for either women or their doctors to feel DCIS, as it rarely is large enough to cause a lump. Nearly all DCIS is detected during routine screening mammograms.

This doesn't mean DCIS is never a problem. About one in 100 women with DCIS actually has invasive cancer cells lurking in her breast ducts, says Partridge. So why are virtually all women with DCIS treated?

"Until you take it all out, you can't know it is only DCIS," Partridge tells WebMD. "In some ways it is incumbent on us as oncologists to take it out to prove it is only DCIS. It is hard to predict who is just DCIS and who is having invasive cancer cells hiding in the DCIS."

And if DCIS comes back, which happens less than 10% of the time, Partridge says there's a 50-50 chance it will come back as invasive cancer.

This makes it sound as though doctors fully understand DCIS. They don't. Doctors treat DCIS when they see it, so nobody is really sure what happens to untreated DCIS.

One thing that is sure is that some women treated for DCIS would never have had serious breast cancer if their DCIS had not been detected, notes H. Gilbert Welch, MD, MPH, director of the VA outcomes group at the Veterans Affairs Medical Center in White River Junction, Vt.

"We know that mammography detects more cancers than would ever become clinically evident," Welch tells WebMD. "You cast a wide net to find early cancers, and that net catches a lot more women than ever would have clinically significant cancers."

How many?

"For every 1,000 women in their 50s who undergo a 10-year course of annual mammography, under a best-case scenario, two would avoid a breast cancer death or have a breast cancer death delayed -- that is the credit side of the balance sheet," Welch says. "On the debit side, 250 to 500 of these women will have at least one false-positive result they will worry about. And about four of these women will be diagnosed with breast cancer unnecessarily -- four women will be overdiagnosed."

DCIS is the poster child for this dilemma, Welch suggests in an editorial accompanying the Partridge report in the Feb. 20 issue of the Journal of the National Cancer Institute. He says women with DCIS are anxious because doctors really don't know what to tell them. He suggests there should be a clinical trial of withholding biopsy until DCIS lesions are large enough to feel.

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