Tomosynthesis: Breast cancer screening method
Early results suggest that it may be a more accurate method of screening, especially if a radiologist combines it with conventional mammography.
Tomosynthesis, which people may refer to as digital breast tomosynthesis (DBT), uses the same technology as a regular mammogram. However, while traditional mammograms are 2-D and provide a flat image, tomosynthesis creates a 3-D image. Standard mammograms and tomosynthesis both use X-rays.
In the past, breast cancer, like other cancers, often had a poor prognosis. Now, however, effective screening and treatment make it possible to remove cancer while it is still in one location and stop it from spreading.
Today, a person who receives a diagnosis of breast cancer in its earliest stage is 99 percent as likely to live for at least 5 more years after their diagnosis compared with someone who does not have this disease.
Mammogram vs. tomosynthesis
Many women in the U.S. are familiar with the mammogram, but few have heard of tomosynthesis.
Tomosynthesis is a way of screening for breast cancer that provides 3-D images.
A mammogram provides an X-ray image of the breast. It can detect cancer even when it is too small to see or feel and has no other signs or symptoms.
Mammograms do not prevent cancer, but they make early detection possible.
Sometimes, a mammogram reveals a lump, but it cannot confirm the type of lump. A person may need further tests, which can be stressful even though a lump is often not cancerous.
This screening procedure is similar to a mammogram, but it produces a 3-D image rather than a flat one. As a result, it may provide more accurate information about whether or not there are any changes in the breast.
The Food and Drug Administration (FDA) approved tomosynthesis for breast screening in 2017.
Research shows that radiologists are highly satisfied with tomosynthesis as a screening tool.
However, this is a new technology, and more evidence is necessary to confirm its usefulness. As a result, only a few hospitals offer tomosynthesis, and it is not yet a standard screening method for breast cancer.
Sometimes, doctors may recommend combining a 2-D mammogram with 3-D tomosynthesis to try to get a more accurate result.
Comparing tomosynthesis with a mammogram
Dimensions: In standard 2-D mammography, the radiologist takes X-rays of each breast from two angles: from top to bottom and from side-to-side. In tomosynthesis 3-D mammography, they take multiple X-rays of each breast from many angles.
Patient experience: During both types of screening, a technologist will position the breast on the plate of the mammography machine. They will then lower the top plate of the machine to compress the breast while taking a picture. The compression only lasts for a few seconds, but it can be uncomfortable.
Taking the image: During tomosynthesis, the X-ray tube moves in an arc around the breast. Over 7 seconds, the machine takes about 11 images of thin slices of the breast from different angles. The machine then transmits the information to a computer, which assembles the data to produce 3-D images of the breast.
Interpreting the images: The 2-D approach of a mammogram can sometimes produce images with overlapping breast tissue that can look like a lump or mass. In some cases, this can lead to a false-positive result.
Mammography takes pictures from just two angles. By taking images from multiple angles, tomosynthesis can give a more accurate result.
What does the research say?
Tomosynthesis may offer more accuracy than a conventional mammogram.
A 2016 review describes tomosynthesis as being more sensitive than 2-D mammography, more likely to provide a clear result the first time, and less likely to produce a false-positive result.
In 2014, the author of an article in the American Journal of Roentgenology noted that using tomosynthesis might reduce recall rates for further testing in the U.S. by 30–40 percent.
The researcher also cited a 2014 Norwegian study, the results of which suggested that screening with tomosynthesis led to a 40-percent increase in the detection of invasive cancer.
A 2014 U.S.-based study evaluating close to 455,000 breast scans found that combining tomosynthesis with mammography led to an increased cancer detection rate and a reduced need to recall people for additional testing compared with mammography alone.
These findings suggest that tomosynthesis may provide more accurate results than a mammogram and that it might make cancer easier to detect in dense breast tissue.
Benefits and risks
Although there is still a need for further studies, evidence shows that tomosynthesis might:
- identify tumors that conventional mammograms alone cannot find
- reduce the risk of a false-positive result leading to further testing
- detect tumors in dense breast tissue that 2-D mammography might miss
Disadvantages of tomosynthesis might include the following:
- it can take longer to interpret the images
- more costly
- it may be difficult to find a facility nearby that offers this type of screening
- it delivers a higher radiation dose than mammography, although it is within the safe limits that the FDA set
While tomosynthesis may improve breast cancer screening, further studies on the risks and benefits are necessary.
Other screening options
There are different ways to screen for breast cancer. Doctors often combine methods for a more accurate result.
The different methods include:
Clinical breast examination: A doctor examines the breasts.
Ultrasound: An ultrasound evaluates any masses that a mammogram or physical examination detect.
MRI scan: Doctors may use an MRI scan to diagnose, evaluate, and assess a mass after surgery or following radiation therapy. They may also sometimes use it to screen a person who is at high risk of breast cancer.
Thermography: This test reveals skin temperature changes that could indicate a tumor.
BRCA testing: This test can show whether a person carries the BRCA1 or BRCA2 gene mutation, either of which can indicate a higher risk of breast cancer. A person with a BRCA gene mutation may need more regular breast screening. A doctor may recommend this test if a person has a family history of breast cancer.
Breast self-examination used to be part of the recommended screening process, but since 2009, the U.S. Preventive Services Task Force no longer advise it. However, women should always be aware of the condition of their breasts and report any unusual changes to their doctor.
For now, 2-D mammography remains the gold standard for breast cancer screening and offers the best way to detect breast cancer early.
Regular screening makes early detection and effective treatment possible.
In their guidelines for the early detection of cancer, the American Cancer Society (ACS) recommend that women have a mammogram:
- annually from age 40–44 years, if they wish
- annually when aged 45–54 years
- annually or every 2 years after the age of 55 years, as long as the woman is in good health and expects to live at least 10 more years
They also recommend that women of all ages know the benefits, limitations, and possible harms of breast cancer screening.
Screening aims to detect:
- calcium deposits in milk ducts and tissues
- lumps or masses
- asymmetric areas
- dense areas in one breast or one area of the breast
- new dense areas that have appeared since a previous mammogram
Around 40 million mammograms take place each year in the U.S.
Find out more here about why breast cancer screening is important.
The outlook for people with breast cancer has improved dramatically over the last few decades, and the chances of survival are far higher now than they were in the past.
Tomosynthesis is a new method of screening that may offer slightly more accuracy than regular mammography, as it provides 3-D rather than 2-D images.
However, according to the ACS, only about 1,000 medical facilities in the U.S. offer tomosynthesis, and it may be more costly than conventional mammography.
The National Cancer Institute warn that insurance companies may not reimburse the costs of tomosynthesis. They note that "some professional groups consider it investigational," and highlight the need for further studies.
In many cases, the additional cost and challenge of accessing 3-D tomosynthesis mammography compared with a standard mammogram may not yet make it worthwhile.