Mammography, X-ray

Radiation-Induced Breast Cancer

Breast cancer cause

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Mammography: An Individual's Estimated Risk that the Examination Itself Will Cause

Radiation-Induced Breast Cancer

From pp.172-181 of the 1996 book Preventing Breast Cancer, by John W.
Gofman, M.D., Ph.D. Adapted for this table by Dr. Gofman, June 9, 1998.


Basis:

Exam is done at an accredited mammography facility.
Mean glandular x-ray dose per view = 0.1 rad (0.1 centi-gray, cGy).
There are two views of each breast per exam.
Combined mean glandular dose to each breast = 0.2 rad (0.2 cGy).

Unrepaired damage to genes from xrays accumulates. Therefore, the risk from
multiple mammograms is the sum of the risk from each individual exam.


Risks below refer to incidence of cancer; risk of mortality is 4x lower.

Age at Exam	Resulting Risk of Mammogram-Induced Breast Cancer.
Any age in 30-34 range	1 exam: 1 chance in about 1,100. 5 exams: 5 chances/1100, or 1 chance in 220.
Any age in 35-49 range	1 exam: 1 chance in about 1,900. 10 exams: 10 chances/1900, or 1 chance in 190.
Any age in 50-64 range	1 exam: 1 chance in about 2,000. 15 exams: 15 chances/2,000, or 1 chance in 133.

We have no data on xray exposure beyond age 64.


The typical exam supposedly gives a total dose of 0.2 rad. Regulations permit mean glandular dose per exam to be three times higher (up to 0.6 rad total per exam). From such doses, every estimate above would be 3x higher.

Some women will be at lower risk per exam, and others at higher risk. There is presently no way to identify which women are most vulnerable to xray-induced cancer.


In all examples above, an individual's chance of NEVER getting mammogram-induced breast-cancer far exceeds the risk of getting mammogram-induced breast-cancer.


Still, a low risk is not "imaginary" or "hypothetical." For instance, every American's chance of NEVER dying from pneumonia or influenza far exceeds the chance of dying from those diseases --- yet every year, 83,000 Americans do die of pneumonia and influenza.


Although the estimates above are necessarily approximate, they can help women and their physicians to evaluate potential harm (not only potential benefit) from multiple mammograms.

Mammograms which turn out to be "false positives" often result in additional xray procedures and risk.

REFERENCES:

From pp.172-181 of the 1996 book Preventing Breast Cancer, by John W.
Gofman, M.D., Ph.D. Adapted for this table by Dr. Gofman, June 9, 1998.

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