There is no scientific evidence that radiation from a mammogram significantly increases the likelihood of getting thyroid cancer. The radiation dose to the thyroid from a mammogram is extremely low. It is equivalent to only 30 minutes of natural background radiation received by all Americans from natural sources. During a mammogram, the thyroid is not exposed to the direct X-ray beam used to image the breast and receives only a tiny amount of scattered X-rays (less than 0.005 milligray).
For annual screening mammography from ages 40-80, the cancer risk from this tiny amount of radiation scattered to the thyroid is incredibly small (less than 1 in 17.1 million women screened). This minute risk should be balanced with the fact that thyroid shield usage could interfere with optimal positioning and could result in artifacts — shadows that might appear on the mammography image — which could impede diagnosis and lead to the need for repeat exams (and repeat exposures). Therefore, use of a thyroid shield during mammography is not recommended.
For more information about thyroid cancer and mammography, please see Summary of Thyroid Cancer Risks Due to Mammography by R. Edward Hendrick, PhD.
Mammography has helped reduce the breast cancer death rate in the United States by nearly a third since 1990. Patients are urged not to put off or forgo necessary breast imaging care. For more information on mammography, please visit www.mammographysaveslives.org.