Breast Cancer and Radiation (Part 2)
With what we know about the effects of radiation on breast tissue, it is ironic that the most widely used breast screening tool, the mammogram, exposes our breasts to ionising radiation! How much of a risk this exposure poses is a question of debate. Dr Samuel Epstein writing in the International Journal of Health Services (2001 31:3) states that “each rad of exposure (increased) breast cancer risk by 1%, resulting in a cumulative 10% increased risk over ten years of pre-menopausal screening, usually from the age of 40 – 50”.
In New Zealand the typical rad exposure during a mammogram is considerably less than that surmised by Epstein, with a typical mammogram (2 shots per breast) exposing a woman to a cumulative total of just over 0.2 cGY. Two yearly mammograms over a decade would give a cumulative exposure of 3.6cGy (rads) per decade. New Zealand code of practice states that a dose of 0.15cGy per single view should not be exceeded in a mammogram. The more your breasts are squashed between the X-ray plates, the lower will be the dose of radiation!
Taking all the factors into consideration, experts still conclude that the low risk of radiation exposure from mammograms is outweighed by increased likelihood of early cancer detection. However, common sense suggests that this equation is altered by age, with premenopausal women being at greatest relative risk from radiation exposure, and also having lowest projected benefit from mammograms (due to their lower absolute risk of developing breast cancer, combined with the increased rate of false negative results due to denser breast tissue). The combined effect of these two variables are a significant reason for women to seriously consider questioning the widespread recommendation of beginning mammograms at the age of 40. (that’s a whole new blog in itself)
Reducing radiation exposure
- Question the necessity of X-rays and CT-scans on any given occasion. Are they absolutely vital?
- Always request that your chest, breasts and abdomen be covered with a lead apron during X-rays – even dental X-rays.
- Resist the dentists suggestion of a dental X-ray at each visit, and save them for when they are absolutely necessary.
- Ask what dosage of radiation you will be exposed to. Be very concerned by radiographers who either wont tell you or tell you they don’t know. Cancel the procedure and go elsewhere!
- Go to specialist radiography centres for procedures involving radiation. They are most likely to have regular and accurate calibration of radiation emitting equipment.
Measuring Radiation
1 Seivert = 100 rads
1 milliSeivert (mSv) = 0.1rad
1 Grey = 1 seivert
1 centriGrey (cGy) = 1 rad
Background radiation 0.5cGy/year (depending on location)
Chest X-ray (1 view) 0.025cGy
Mammogram (4 views) 0.5cGy
Fully body CT (breasts 6+ cGy
exposure)
In terms of breast tissue exposure from mammograms, 1 Grey equals 1 Seivert
To Your Wellbeing…
Lynda Wharton
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