Last Modified: June 11, 2009
Dear OncoLink "Ask The Experts,"
I was diagnosed 2 years ago with breast cancer. I had yearly mammograms and lived a healthy life. Eight months after my last mammogram, I found a lump. Following lumpectomy, the path report indicated a 6.3 cm tumor, the extent of which did not show [up] on the MRI or ultrasound. My question is, what research is being done for false positive mammograms, as my understanding is that they are only 70-80% accurate? I have been searching for research, unsuccessfully.
Carolyn Vachani RN, MSN, AOCN, OncoLink's Nurse Educator, responds:
Research is being done all the time on ways to improve accuracy of mammograms. What you describe is a false negative, meaning the mammogram was negative for cancer, but there was actually a tumor present. Unfortunately, the false negative rate with mammogram is in the 20-30% range- either because the tumor was missed due to dense breast tissue or other factors, or the tumor is “mammographically occult”, meaning it cannot be seen on a mammogram. This is why, if a woman or her doctor detects a lump, but nothing is found on mammogram, further testing must be done to identify the lump. The other side of the coin are false positives, where the mammogram is read as having an abnormality that looks like cancer, but further tests (ultrasound, MRI, biopsy) prove it is benign.
In recent years, digital mammography was looked at for screening. This technology takes a similar image to film mammography, but uses digital technology. This allows for digital storage and transfer of images, higher resolution thanks to the digital technology, images that can be manipulated to enhance visualization of abnormalities, and less waiting time for the patient, since films do not need to be developed. The main disadvantage to digital machines is the cost, which can be up to four times as much as a standard film machine. Many assumed this technology would lead to improved diagnosis, but it is an example of why clinical studies are so important. The Digital Mammographic Imaging Screening Trial (http://www.cancer.gov/dmist) enrolled almost 50,000 women and compared film mammography to digital. The study found that for most women, there was no difference in detecting breast cancer with digital technology. There were a few groups that did have superior detection with digital technology - young, premenopausal and perimenopausal women, and those with dense breast tissue.
MRI has been studied, but it has a much higher false positive rate, leading to many unnecessary biopsies and anxiety, not to mention that the cost and availability of these tests limits its use for the general public. MRI is, however, used for some high risk populations in conjunction with mammogram.
But, rest assured that the breast radiologists are always looking for ways to improve their technology. Unfortunately, no test is perfect, which you learned the hard way. Tomotherapy, scintimammography and contrast-enhanced mammography are just some of the technologies being explored. A few of these studies are referenced below. You can look for current breast imaging studies at clinicaltrials.gov.