Mammography

Mammography (also called mastography) is the process of using low-energy X-rays (usually around 30 kVp) to examine the human breast for diagnosis and screening. The goal of mammography is the early detection of breast cancer, typically through detection of characteristic masses or microcalcifications. Mammography (also called mastography) is the process of using low-energy X-rays (usually around 30 kVp) to examine the human breast for diagnosis and screening. The goal of mammography is the early detection of breast cancer, typically through detection of characteristic masses or microcalcifications. As with all X-rays, mammograms use doses of ionizing radiation to create images. These images are then analyzed for abnormal findings. It is usual to employ lower-energy X-rays, typically Mo (K-shell x-ray energies of 17.5 and 19.6 keV) and Rh (20.2 and 22.7 keV) than those used for radiography of bones. Ultrasound, ductography, positron emission mammography (PEM), and magnetic resonance imaging (MRI) are adjuncts to mammography. Ultrasound is typically used for further evaluation of masses found on mammography or palpable masses not seen on mammograms. Ductograms are still used in some institutions for evaluation of bloody nipple discharge when the mammogram is non-diagnostic. MRI can be useful for further evaluation of questionable findings, as well as for screening pre-surgical evaluation in patients with known breast cancer, in order to detect additional lesions that might change the surgical approach, for example, from breast-conserving lumpectomy to mastectomy. Other procedures being investigated include tomosynthesis. For the average woman, the U.S. Preventive Services Task Force recommends (2016) mammography every two years between the ages of 50 and 74, concluding that 'the benefit of screening mammography outweighs the harms by at least a moderate amount from age 50 to 74 years and is greatest for women in their 60s'. The American College of Radiology and American Cancer Society recommend yearly screening mammography starting at age 40. The Canadian Task Force on Preventive Health Care (2012) and the European Cancer Observatory (2011) recommend mammography every 2 to 3 years between ages 50 and 69. These task force reports point out that in addition to unnecessary surgery and anxiety, the risks of more frequent mammograms include a small but significant increase in breast cancer induced by radiation. Additionally, mammograms should not be performed with increased frequency in patients undergoing breast surgery, including breast enlargement, mastopexy, and breast reduction. The Cochrane Collaboration (2013) concluded after ten years that trials with adequate randomization did not find an effect of mammography screening on total cancer mortality, including breast cancer. The authors of this Cochrane review write: 'If we assume that screening reduces breast cancer mortality by 15% and that overdiagnosis and over-treatment is at 30%, it means that for every 2,000 women invited for screening throughout 10 years, one will avoid dying of breast cancer and 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily. Furthermore, more than 200 women will experience important psychological distress including anxiety and uncertainty for years because of false positive findings.' The authors conclude that the time has come to re-assess whether universal mammography screening should be recommended for any age group. They state that universal screening may not be reasonable. The Nordic Cochrane Collection updated research in 2012 and stated that advances in diagnosis and treatment make mammography screening less effective today, rendering it “no longer effective.” They conclude that “it therefore no longer seems reasonable to attend” for breast cancer screening at any age, and warn of misleading information on the internet. Mammography has a false-negative (missed cancer) rate of at least ten percent. This is partly due to dense tissue obscuring the cancer and the appearance of cancer on mammograms having a large overlap with the appearance of normal tissue. A meta-analysis review of programs in countries with organized screening found a 52% over-diagnosis rate. The use of mammography as a screening tool for the detection of early breast cancer in otherwise healthy women without symptoms is controversial. Keen and Keen indicated that repeated mammography starting at age fifty saves about 1.8 lives over 15 years for every 1,000 women screened. This result has to be seen against the adverse effects of errors in diagnosis, over-treatment, and radiation exposure. The Cochrane analysis of screening indicates that it is 'not clear whether screening does more good than harm'. According to their analysis, 1 in 2,000 women will have her life prolonged by 10 years of screening, while 10 healthy women will undergo unnecessary breast cancer treatment. Additionally, 200 women will suffer from significant psychological stress due to false positive results. Newman points out that screening mammography does not reduce death overall, but causes significant harm by inflicting cancer scare and unnecessary surgical interventions. The Nordic Cochrane Collection notes that advances in diagnosis and treatment of breast cancer may make breast cancer screening no longer effective in decreasing death from breast cancer, and therefore no longer recommend routine screening for healthy women as the risks might outweigh the benefits. Often women are quite distressed to be called back for a diagnostic mammogram. Most of these recalls will be false positive results. Of every 1,000 U.S. women who are screened, about 7% will be called back for a diagnostic session (although some studies estimate the number to be closer to 10% to 15%). About 10 of these individuals will be referred for a biopsy; the remaining 60 cases are found to be of benign cause. Of the 10 referred for biopsy, about 3.5 will have cancer and 6.5 will not. Of the 3.5 who have cancer, about 2 will have an early stage cancer that will be cured after treatment. Mammography may also produce false negatives. Estimates of the numbers of cancers missed by mammography are usually around 20%. Reasons for not seeing the cancer include observer error, but more frequently it is because the cancer is hidden by other dense tissue in the breast, and even after retrospective review of the mammogram, the cancer cannot be seen. Furthermore, one form of breast cancer, lobular cancer, has a growth pattern that produces shadows on the mammogram that are indistinguishable from normal breast tissue. The Cochrane Collaboration states that the best quality evidence does not demonstrate a reduction in mortality or a reduction in mortality from all types of cancer from screening mammography.