This week’s cancer news features a study in the current issue of the Archives of Internal Medicine, first reported by Reuters:
CHICAGO (Reuters) — Radiation from CT scans done in 2007 will cause 29,000 cancers and kill nearly 15,000 Americans, researchers said on Monday:
…The findings, published in the Archives of Internal Medicine, add to mounting evidence that Americans are overexposed to radiation from diagnostic tests, especially from a specialized kind of X-ray called a computed tomography, or CT, scan.
The risks of radiation from CT scanning will almost certainly add to the current confusion and concerns about the risks of breast cancer screening.
Mammography differs from CT scanning in several important ways:
1. Mammograms involve much less radiation exposure than CT scans.
According to the American Cancer Society, a typical mammogram uses between 0.1 to 0.2 mSV per image. So even if multiple images are taken of each breast, the total dose remains under 1 mSV.
Another source, the Health Physics Society, estimates a dose of 0.7 mSV per mammogram. So if a woman were to have a screening mammogram every other year between the ages of 40 and 49, she’d receive approximately 3.5 mSV in total from those procedures.
By contrast, a single CT scan involves over a 10-fold greater amount of radiation (such as 8 mSV for a CT of the chest, 10 mSV for a CT of the abdomen) according to the Health Physics Society fact sheet.
2. Mammography is well-regulated by the Food and Drug Administration (FDA) and other agencies.
The Mammography Quality Standards Act (MQSA) requires mammography facilities across the nation to meet uniform quality standards. The law, first passed in October, 1992, requires all mammography facilities to 1) be accredited by an FDA-approved accreditation body, 2) be certified by FDA, or its State, as meeting the standards, 3) undergo an annual MQSA inspection, and 4) prominently display the certificate issued by the agency.
3. Women who undergo screening mammograms can control when and where they get this procedure.
Screening mammograms are elective by nature; a woman can choose an accredited screening facility and, in advance, learn something about its reputation and screening methods. Most women between the ages of 40 and 50 are capable of tracking their mammograms, whether they choose to have those annually, biennially, or less often.
Many CT scans are ordered for patients who are in the hospital — a very different sort of circumstance. Many hospitalized patients don’t feel well, don’t understand what’s happening to them and/or lack the needed assertiveness or language skills to ask about a scan before it’s done.
Summary:
Mammography is a relatively safe and highly-regulated procedure in the U.S. The recent news on risks from radiation in CT scanning should not confound the discussion of breast cancer screening.