Breast Cancer and Mammography

Luciano Fernandes Chala

Radiologist, Fleury Medicina e Saúde Group

Doctor of Medical Sciences, Faculty of Medicine of the University of São Paulo

Member of the Scientific Committee of the Breast Chapter, São Paulo Society of Radiology

Member of the National Mammography Commission, Brazilian College of Radiology

Member of the Commission of Accreditation in Imaging Diagnosis, Brazilian College of Radiology

Breast cancer is the most common cancer in women in Brazil and the world. The Pink October is a movement created in the 1990s that aims to engage the population in controlling the disease. So it is a great time to remember the importance of mammography and clarify questions about it.

From the 1970s, a progressive reduction in mortality from breast cancer began, especially in developed countries. That has been attributed to the early detection of the disease in mammography screening and advances in treatment. Several studies have shown that periodic mammography is associated with a reduction in mortality from the disease; in the Independent UK Panel’s meta-analysis, this reduction was estimated at 20%. For this reason, several medical organizations recommend that women get a mammogram every year after age 40.

One of the legitimate fears of women is whether the repeated use of mammography can paradoxically cause breast cancer. No study has directly demonstrated that women who have mammography have more breast cancer than those who do not and studies based on mathematical models have shown the number of deaths averted by the use of mammography is much higher than the theoretical risk of cancer induced by exam. Also, the radiation dose used in mammography is extremely low and has been significantly reduced with advances in the technology of the exam, especially the introduction of full-field digital mammography. To get an idea, annually we receive from unavoidable natural sources of ionizing radiation, an amount of radiation equivalent to 4 to 6 mammograms. Therefore, there is no reason for women to stop having their annual mammogram because of the fear of the exam causing breast cancer. However, this does not mean that we do not have to be careful when performing the mammogram. Any action that reduces the dose of radiation and maintains the quality is welcome, this includes making it only when necessary and in places with strict quality control of the equipment.

Another topic related to mammography radiation that emerged in the media was the supposed association between mammography and the increase in the incidence of thyroid cancer and, therefore, the need for the use of thyroid protectors during the examination, which may impair its performance and compromise diagnostic efficiency. This association has no reasonable scientific basis. Also, according to statistics from the US National Cancer Institute, the incidence of thyroid cancer has increased since 1998 at a similar rate between women and men, and the latter does not perform regular mammograms. Finally, the dose of radiation received by the thyroid during mammography is equivalent to 30 minutes of exposure to the inevitable natural sources of radiation.

Several medical societies such as the Brazilian College of Radiology and Diagnosis, the American College of Radiology, the Department of Health and the Association of Radiologists of Canada and the American Thyroid Association have issued opinions not recommending the use of the thyroid protector during the exam. In conclusion, there is no reason for the woman to stop having the mammogram or have it with a thyroid shield because of the fear of thyroid cancer induced by mammography radiation.