Follow-up mammograms may fail to detect cancer

Mammograms performed within a short span of the first mammogram that shows lumps to be “probably benign” often fail to detect cancer. Mammography is a special type of X-ray that is used for detailed images of the breast. Successful treatment of breast cancer depends on early diagnosis, and mammography as a technique plays a major role in its early detection. It can show changes in the breast well before they are actually felt. Biopsy (sampling of tissue) of an abnormality may be done to further confirm if the tissue is cancerous or not. Researchers in America examined the accuracy of 45,007 initial short-interval follow-up mammograms from the Breast Cancer Surveillance Consortium interpreted 3–9 months after the first mammogram revealed lumps thought to be benign. The mammograms were linked with patient characteristics and breast cancer diagnoses within 12 months. A subset of mammograms was also linked to characteristics of the radiologist who read the X-rays. It was found that breast cancer was diagnosed in less than one per cent of the women within six months and in a little more than one per cent within 12 months. Follow-up mammograms missed roughly 17 per cent of the cancers diagnosed within six months and about 40 per cent of those diagnosed within 12 months. One reason for these findings could be that cancers assessed as probably benign may not grow as rapidly as cancers that appear more suspicious. Also, a radiologist who interprets the follow-up study may get a false sense of security from the fact that the initial results were considered to be benign.