According to the results of a study published in the International Journal of Cancer, women who have received radiation to the chest for the treatment of cancer or for the diagnosis of tuberculosis or pneumonia have an increased risk of developing breast cancer.
Exposure of the chest to high or intermediate levels of radiation is known to increase the risk of breast cancer, but there is less information about the risk posed by lower doses of radiation.
To explore the relationship between exposure to medical radiation and risk of breast cancer, researchers conducted a study among women in Ontario, Canada, and Melbourne and Sydney, Australia. The study enrolled 2,254 women with breast cancer and 3,431 women without breast cancer.
The study collected self-reported information about therapeutic and diagnostic radiation exposure to the chest (other than mammograms). Therapeutic radiation included radiation given to treat tuberculosis, cancer, acne, mastitis, hemangioma, or other conditions. Diagnostic radiation included radiation used for heart catheterization, monitoring of scoliosis, and diagnosis of tuberculosis, pneumonia, back problems, gastrointestinal problems, and other conditions.
- Radiation to the chest for the treatment of cancer was linked with a more than threefold increased risk of breast cancer.
- Radiation to the chest for the treatment of acne or other skin conditions was linked with a roughly twofold increased risk of breast cancer. However, this result did not meet the criteria for statistical significance, suggesting that it could have occurred by chance alone.
- Therapeutic radiation to the chest carried the greatest risk if it was received before the age of 20 or during the 1960s. Risk also increased with an increasing number of exposures.
- Radiation to the chest for the diagnosis of either tuberculosis or pneumonia was linked with a roughly twofold increased risk of breast cancer. Among women who received chest X-rays for these purposes, risk was greatest if the X-ray was received before the age of 20 or before 1960. Risk also increased with an increasing number of chest X-rays.
- Overall, chest X-rays used to diagnosis conditions other than tuberculosis or pneumonia were not linked with an increased breast cancer risk.
- The risks associated with diagnostic chest X-rays were similar for women with and without a family history of breast cancer.
The researchers conclude, “Given the widespread and increasing use of medical diagnostic radiation, continued surveillance of breast cancer risk is warranted, particularly in women at specific genetic risk, such as those carrying mutations in BRCA1 or BRCA2.”
Reference: John EM, Phipps AI, Knight JA et al. Medical radiation exposure and breast cancer risk: findings from the Breast Cancer Family Registry. International Journal of Cancer [early online publication]. March 19, 2007.