Tuesday Nov 25, 2008 (foodconsumer.org) -- A recent study found that women who have subjected themselves once every two years to mammogram screening are more likely to be diagnosed with breast cancer than those who have not.   And researchers said the difference was caused largely by spontaneous regression in the control group.

What is your first impression for this finding?   I guess most of you would naturally think mammogram screening raises the risk of breast cancer.   After all, there is a reason for this.    The U.S. government has already officially recognized x-ray radiation used for mammograms as a human carcinogen.

But if you read a couple of news reports on the study including the one by the New York Times, researchers part or not part of the research team did  not mention the potential risk from x-ray.

Instead, they proposed a new theory that says that the lower incidence of breast cancer found in the women who received the screening less frequently were actually experiencing some spontaneous regression, that is, they actually developed the disease at certain point in time, and then their body got rid of it without treatment or in this case without multiple mammogram screenings.

No one could deny that spontaneous regression does occur in some cases of cancer although what affects the outcome remains unknown.   But how many dare to think that the very risk probably comes from x-ray or radiation based mammography.

Some researchers mentioned that it is likely for women who have received multiple mammogram screenings to receive biopsy and unnecessary treatments such as hormone therapy, which they said may actually lead to the development of breast cancer. They and all others including the news media failed to point out that x-ray used in mammography is a proven carcinogen!

The study was conducted by Per-Henrik Zahl, M.D., Ph.D., of the Norwegian Institute of Public Health, Oslo, and colleagues. The researchers examined breast cancer rates among 119,472 women age 50 to 64 who were all invited to participate in three rounds of mammogram screening between 1996 and 2001 as part of the Norwegian Breast Cancer Screening program. They compared these to the rates among 109,784 age 50 to 64 in 1992 who did not receive any screening after the year.

Then the researchers of the study examined all the women once using mammography to see who had had breast cancer and they found that the cumulative incidence of invasive breast cancer were 22 percent higher in the group screened three times during the six year period compared to the control.  

The study was reported in November 24 2008 issue of Archives of Internal Medicine.

"Although many clinicians may be skeptical of the idea, the excess incidence associated with repeated mammography demands that spontaneous regression be considered carefully," the researchers said.

They did not talk about the risk of x-ray.

"Despite the appeal of early detection of breast cancer, uncertainty about the value of mammography continues," wrote Robert M. Kaplan, Ph.D., of the University of California, Los Angeles, and Franz Porzsolt, M.D., Ph.D., of Clincal Economics University of Ulm, Germany, in an accompanying editorial.

"Perhaps the most important concern raised by the study by Zahl et al is that it highlights how surprisingly little we know about what happens to untreated patients with breast cancer," Drs. Kaplan and Porzsolt continued.

He did not mention the potential risk of x-ray either.

Those who want to know the risk of x-ray may do some homework.   Just recently one more study published in the Dec 2008 issue of Breast Cancer Research and Treatment found that one chest x-ray before age 30 increased the risk of breast cancer by 80 percent in BRCA1 carriers.

The take-home message is that 1) x-ray based mammogram screening increases breast cancer risk; 2) the screening may suppress spontaneous regression. The former is a certainty and the latter is a possibility.

The bottom-line is that x-ray is the most studied and potent human carcinogen.   It can cause cancer and there is no safe threshold meaning any dose increases some risk, many scientists would agree.   Dr. John Gofman, a distinguished nuclear physician, said x-ray is responsible at least partially for 75 percent of breast cancer cases.