In cancer care, radiation oncologists use a special type of energy in the form of radiation to disrupt the growth of cancer cells. The energy of radiation is also occasionally used to treat other conditions involving rapid or unwanted cell growth.
At much lower levels, a radiologist uses radiation to create images of tissue, called diagnostic radiation. Chest x-rays (to look at lung tissue) and mammograms are examples of this use of radiation.
In all these situations, normal cells are exposed to radiation. When normal cells are exposed to radiation, the energy can actually hurt the cells or cause them to become cancerous. In the case of radiation therapy for cancer, this means that the radiation used to treat one cancer could trigger the development of another, different cancer that is diagnosed years later. This is why radiation oncologists use techniques to precisely aim radiation therapy to cancer tissue only. It is also why when getting certain x-rays, people are asked to wear a "lead shield" that actually blocks x-rays from reaching parts of the body that are not being studied.
Earlier research has shown that moderate-dose and high-dose radiation exposure with radiation therapy for other cancers or conditions can substantially increase a woman's chance of developing breast cancer years later. The researchers in this study wanted to determine whether low doses of radiation exposure, either given as therapy for conditions such as cancer, or from x-ray studies, increased breast cancer risk as well.
In the case of women who received low-dose radiation treatment for a previous cancer, the risk of developing breast cancer years later was about 3 and 1/2 times higher than the breast cancer risk of women who did not receive radiation therapy. This increased risk of breast cancer from low-dose radiation exposure was greatest in women who carried genes associated with breast cancer. One bit of good news from this research was that low-dose radiation exposure from x-rays was, except in a few special circumstances, NOT associated with increased breast cancer risk.
In addition to radiation therapy, other cancer treatments, such as chemotherapy, can increase a woman's risk of developing treatment-related medical conditions, including breast cancer, years after receiving the earlier cancer treatment. If you have received radiation therapy or other cancer treatments in the past, it's important that your doctor is familiar with your medical history and understands any treatment-related risks you may have. Together, you and your doctor can plan how best to monitor and screen to manage any longer-term effects. You should do all that you can to minimize your risk of another cancer.
For more information about radiation therapy and chemotherapy, visit the breastcancer.org Treatments & Side Effects section.
NEW YORK (Reuters Health) - Some forms of low-dose radiation treatment may increase the risk of breast cancer, particularly in genetically susceptible women, according to a report in the International Journal of Cancer.
Moderate- to high-dose radiation therapy has been shown to increase the risk of breast cancer, the authors explain, but it remains uncertain whether the risk extends to low-dose radiation, such as diagnostic chest X-rays.
Dr. Esther M. John from the Northern California Cancer Center, Fremont, and associates investigated the association between therapeutic or diagnostic radiation exposure and breast cancer using data from the Breast Cancer Family Registry. Self-reported information was available for 2,254 breast cancer patients and 3,431 healthy women, which included the sisters of the patients or women from the general population.
Radiation treatment of a previous cancer increased the risk of breast cancer by 3.55-fold, the investigators report. They also noted a trend toward higher breast cancer risk among women who received radiotherapy for acne or other skin conditions.
Women who had diagnostic chest X-rays for tuberculosis or pneumonia had more than twice the normal risk of breast cancer.
Women who underwent radiation for heart catheterization, spine problems, gastrointestinal illness or other unspecified chest X-rays were not at increased risk for breast cancer, the researchers note.
"To our knowledge," John and colleagues note, "this is the largest population-based case-control study conducted to date exploring associations with radiation exposure for conditions that have not been the focus of follow-up studies (i.e., radiation treatment for acne or pneumonia). Given the low prevalence of such exposures, large sample sizes are needed to detect associations in a case-control study."
"The findings of elevated breast cancer risk in women exposed to radiation for pneumonia and acne presented here warrant further investigation," they conclude.
SOURCE: International Journal of Cancer, July 15, 2007.
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