Benefits and drawbacks of mammography
Breast Cancer detection with Mammography basically utilizes a low dose X-ray as the initial diagnostic tool. As with all X-rays, there are potential drawbacks to the procedure as well. Frequent X-rays of any kind are really not recommended for young people. Nonetheless, mammography is the primary factor in breast cancer mortality reduction, and the expected benefits far outweigh the risks. The mammogram is also indicated if a palpable mass is detected by either the patient, referring clinician, or radiologist.
Just so you know, this page is old, from around year 2000. The new information about mammography screening programs is here.
Women under 30 are more likely to receive breast ultrasound
For women less than 30 years of age, ultrasound is the preferred modality. Women between 30 and 40 may be given the mammography X-ray, but only with a prescription. Diagnostic mammography is indicated whenever there are abnormal results from an initial breast cancer screening, such as a probable benign lesion of at least BI-RADS category 3.
Follow up breast mammograms may be recommended in some cases
Diagnostic mammography at 6 months intervals is recommended as follow up for any recent breast preservation surgery for cancer. Scans should be made every 6 months for the first five years for the affected breast and every year for the non-affected breast. Other breast problems such as spontaneous nipple discharge, personal history of breast cancer, or other histological anomalies from a previous biopsy such as LCIS or atypical hyperplasia, require a followup mammogram. (LCIS refers to ‘Lobular carcinoma in situ’ It is not a cancer, but its presence means that there may be increased risk for breast cancer development in the future.)
Drawbacks of mammography such as false negatives and false positives
Mammograms are sensitive up to about 90% of the breast, which means there is about a 10% chance that a small tumor is present, but not detected. This is called a ‘false negative’. A ‘false positive’ refers to a finding of an anomaly of some kind, but it turns out not to be cancer. This can result in all kinds of unnecessary interventions.
Radiation risks of breast cancer X-ray
The average glandular dose of radiation for 2 exposures with a grid is about 1.6 to 2 mGy (0.16-0.2 rad). So, if one could mathematically project that for an annual irradiation of 100000 women between the ages of 40 and 50, over a then year period, this amount of irradiation could theoretically cause between 1 and 8 mortalities. However, one has to compare this to the theoretical mortality rate due to breast cancer if screening mammography were not utilized. Estimates range from increased breast cancer mortality by 8 to 25 times, and in some cases those estimates range from 65 to 200 times.
To put the radiation risk into perspective, the average dose of radiation from a breast X-ray is about the same as background radiation exposure during a round trip by airplane from Denver to New-York, or travelling 1000 km in a car. Clearly, the benefits of breast cancer screening vastly outweigh the potential health risks due to radiation exposure.
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