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27 September 2017

3D mammography, also known as tomosynthesis, is becoming more widely available. The thin “slices” (images) make it easier to spot cancers in patients with dense breast tissue. In addition, the use of 3D mammography can decrease the rate of “callbacks” – additional images that are often recommended after a screening mammogram due to uncertainty about the findings. Callbacks are more common in women with dense breast tissue. One concern about tomosynthesis is that it might find too much – not everything that is found will be dangerous, and this can result in over diagnosis and over treatment. In addition, a slightly higher dose of radiation exposure is required with 3D imaging in some facilities.

In 2005, the DMIST trial results were published in the New England Journal of Medicine – this study compared the older film screen mammography to digital mammography and found that digital mammograms were more accurate for women under the age of 50, women with dense breast tissue, and those who were pre- or peri-menopausal. Digital mammograms are now standard across most of the country.

The TMIST (Tomosynthesis Mammographic Imaging Screening Trial) trial will compare 3D mammography 2D digital mammography. Rates of cancer detection, callbacks, and procedures (such as biopsies) will be monitored. In addition to evaluating the performance of the imaging technology, the study will attempt to identify biological factors associated with breast cancer risk – patients who participate in the study will be asked to provide a buccal (cheek) swab and blood sample.

The study plans to enroll approximately 165,000 women at approximately 100 centers across the country. Additional information about the study and participating centers is available at the following sites:

National Cancer Institute
ECOG-ACRIN (cooperative group sponsoring the trial)
ClinicalTrials.gov

 

An Oklahoma mayor underwent a 3D mammogram (tomosynthesis) as part of a hospital promotion. She was diagnosed with ductal carcinoma in-situ (DCIS, also known as Stage 0 breast cancer) and she stated that the study “…saved my life.” She also recommended that women make sure to obtain a 3D mammogram. The story noted that tomosynthesis “virtually eliminates” the need for additional testing, and that early detection makes it less likely that the patient will need to undergo chemotherapy or radiation.

Here are a few errors in the story:

Statement: the mammogram saved my life
Fact: survival from breast cancer depends on many factors. The survival rate for patients with DCIS, regardless of treatment, is close to 97%. For invasive cancers, survival rates depend on stage as well as tumor biology. Small breast cancers “caught early” can still be lethal. It’s not the cancer in the breast that kills, it’s the cancer that gets to other areas of the body. Small tumors can and do spread.

Statement: early detection makes it less likely that a patient will need chemotherapy
Fact: the need for chemotherapy depends on tumor stage as well as tumor biology. As noted above, some very small, early stage breast cancers are very aggressive and have a high likelihood of spread, so chemotherapy is recommended. This is especially true for “triple negative” and “Her2/neu over-expressed” breast cancer subtypes.

Statement: early detection makes it less likely that a patient will need radiation therapy
Fact: radiation therapy is a standard recommendation for women with early stage breast cancer who undergo a lumpectomy. Since most women with early stage breast cancer are candidates for a lumpectomy, this statement simply doesn’t make any sense.

Statement: tomosynthesis “virtually eliminates” the need for additional imaging
Fact: while tomosynthesis can reduce the likelihood of needing additional views (“callback”) especially in women with dense breast tissue, diagnostic imaging with possible biopsy are still recommended when a concerning abnormality is seen.

While I certainly wish Ms. Noble well, stories like this always make me cringe, because they over-simplify a very complex situation. Here are some posts from Health News Review with some additional information:
Mayor: 3D Mammogram Saved My Life
3D Mammography and False Hope