Can Mammogram Radiation Cause Breast Cancer?

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Over the last few decades, our radiation exposure has nearly doubled, thanks almost exclusively to medical sources, such as CT scans. We’ve known that higher-dose radiation, like CT scans and angiograms, can cause breaks in our DNA, but now we know that mammograms can, too. You can find X-ray induced DNA damage in white blood cells drawn from women right after her mammogram.

That’s amazing they can find evidence of DNA breaks; I mean, how much blood is there in the breast in the first place? And then you squeeze it out during the procedure, and then it mixes with the unexposed blood from the rest of the body, and you can still pick up the DNA damage circulating throughout her system. So, what they found “underestimate[s]” the DNA damage in the breast tissue itself.

But, doctors tell women, “There is nothing to worry about.” Just a few extra cases of breast cancer are caused by mammograms. Wait; what? Mammograms causing breast cancer? Yes. The “risk of radiation-induced breast cancer” from modern, low-dose digital mammograms depends on how often you get screened, and at what age you start. “For a [group] of 100 000 women…screened annually from age 40 to 55 years and [every other year until] age 74…, it is predicted that there will be 86 cancers induced and 11 deaths due to radiation-induced breast cancer.” Meaning they estimate 11 of those women will die from breast cancer that they would never have gotten if they decided not to get mammograms—not expose themselves to that radiation. They even calculated the lifetime risk of developing a radiation-induced breast cancer after just getting a single mammogram.

Women with large breasts may carry additional risk, because their mammograms may require additional views, and the greater radiation dose is expected to translate into “a greater risk for radiation-induced breast cancer and breast cancer death”—as much as triple the lifetime attributable risk of developing breast cancer because of the mammogram radiation exposure.

The earlier one starts screening, the higher the risk as well, since there’s more time for a cancer to grow. This comes up for women with BRCA gene mutations, for whom screening is sometimes recommended starting in their twenties. But, at that age, mammograms may cause as many breast cancer deaths as they prevent. A net benefit would be expected at 35 years old, though, and likely the same for women without BRCA mutations. Yes, “The risk of radiation-induced cancer from mammography is not negligible, [but] the potential for mortality benefit is generally considered to outweigh the risk of death from radiation-induced [breast cancer] attributed to mammography screening”—”a benefit-to-risk ratio in lives of” 10 to one or more.

Now, these estimates on how much breast cancer mammogram X-rays may cause relies “heavily on data from the atomic bomb survivors,” who were exposed more to gamma rays, which are like high-energy X-rays. But, it turns out the lower energy X-rays used in mammography are even worse—”approximately four times…more effective in causing mutational damage than higher energy X-rays.” And, “[s]ince current radiation risk estimates are based on the effects of…gamma [rays], this implies that the risks of radiation-induced breast cancers [from] mammography X-rays” is four times worse than previously estimated. But, even if that were true, the benefit-to-risk ratio would still favor mammograms—which is why you see editorials in radiology journals like this: “concern about radiation exposure should not prevent [a woman] from undergoing life-saving mammography screening.”

But: “No trial has ever shown an overall mortality benefit from screening mammography. Thus, if there is a detrimental effect of radiation exposure from mammography, even a small effect could offset [the benefits].”

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Image credit: AlarconBenthos via pixabay. Image has been modified.

Motion graphics by Avocado Video

• BRCA genes
• breast cancer
• breast cancer survival
• cancer
• CT scan
• DNA damage
• lifespan
• longevity
• mammograms
• mortality
• radiation
• white blood cell count
• women's health
• X-rays