Mammography Risks Part 5

Since that nagging question, “Do mammogram x-rays add to the risk of developing breast cancer?” bothers many of us health conscious folks, we’ve been looking at the various perspectives in answer to that question.

We covered the main stream reasoning and thinking in the previous blog posts which you may review here:

• Part 1
• Part 2
• Part 3
• Part 4

In this issue we will look at two research experiments that pose a different perspective.

First let’s look at a study done by the Radiation Biophysics Group, School of Physics and Astronomy, The University of Birmingham, Birmingham B15 2TT, United Kingdom.

This group exposed three different sets of human skin fibroblast cells to three types of radiation and then checked the cells to see if they became cancerous.

Using isolated cells in a study is called “in vitro”, meaning this testing was not performed on a person, but rather in a test tube or plate.

These are the types of radiation that they used:

High energy source simulation:

1. Quality of radiation that the atomic bomb survivors were exposed to.

2. 2.2 MeV electrons from a strontium-90/yttrium-90 (90Sr/90Y) radioactive source.

Both of these types of radiation produced the same amount of cancer in the isolated human skin fibroblasts.

Mammography source:

3. 29 kVp X rays which are used for mammography screening

When they analyzed their data they made this observation:

“The increased potential of low-energy X rays to induce neoplastic (cancerous) transformation is clearly seen. Mammography X rays are 4.4 plus or minus 2.0 (SE) times more effective at inducing neoplastic transformations of CGL1 cells in vitro than high-energy electrons for low absorbed doses.”

“This suggests that the risks associated with mammography screening may be approximately five times higher than previously assumed and that the risk–benefit relationship of mammography exposures may need to be re-examined.”

Of course, this type of research cannot be performed on women and we don’t know for sure how to interpret this kind of in vitro testing with what actually occurs in the human body with its repair mechanisms.

However, it does give us some information to ponder.

This second research project gets even more interesting.

At the Lawrence Berkeley National Laboratory (Berkeley Lab) cell biologist Mary Helen Barcellos-Hoff transplanted a special line of nonmalignant breast cells that had not been irradiated into mammary glands that had been exposed to x-rays. Nevertheless almost 75 percent of the transplanted cells developed tumors.

Did you get that? Cells that had not been exposed to any x-rays became cancerous when they were placed in an environment of breast glands that had been x-rayed.

For a control group Barcellos-Hoff transplanted the same type of cells into nonirradiated mice breast tissue. Only 20% of those cells became cancerous.

So what does this mean? Somehow the environment surrounding a cell has an effect on whether the cell becomes cancerous. In other words something besides genetic mutations (changes in DNA) can induce cancer in cells.

A network of fibrous and globular proteins (called the extracellular matrix (ECM), surrounds each breast cell. This tissue surrounding the cell sends signals to the cell. Proper communications between the cell and its microenvironment are essential for normal functioning.

“Ionizing radiation is like a wound, in that it produces a defensive response from the affected tissue. Usually this helps to protect undamaged cells and eliminates those that have become abnormal,” Barcellos-Hoff says. “However, if there is too much damage, the defense response can become a problem.”

As an example of this defense response, consider what happens to the skin when exposed to sunlight. Just the right amount of exposure stimulates the skin to produce more melanin which helps to prevent skin damage when exposed to sunlight in the future.

But if someone stays out in the sun too long, the skin gets burned and damaged.

When breast tissue is exposed to low doses of radiation the surrounding tissue signals the cells to prevent damage to the DNA. If the radiation exposure goes higher, the cells get the wrong message which then can allow mutations and cancer to develop.

In an on-going study Barcellos-Hoff and her team have preliminary evidence that human breast cells exposed to radiation have difficulty communicating between the tissue and cell. This abnormal activity is typical of cancer cells.

So these two studies increase our distrust of mammograms.

Is there an alternative way to detect breast cancer in its early stages that doesn’t carry risks of actually causing breast cancer?

We will address that question in the next blog. So stay tuned.

Blessings,

Dr. Jo

P.S. Sorry that these articles on mammography have been a bit technical. I felt that you needed to know the technical parts so you could make the best informed decisions for yourself.

References:

RADIATION RESEARCH 162, 120–127 (2004)

0033-7587/04 $15.00

q 2004 by Radiation Research Society.

All rights of reproduction in any form reserved

NEW FINDINGS ON BREAST CANCER REPORTED AT AAAS

Lynn Yarris, (510)486-5375, lcyarris@lbl.gov