Comparing mammography and thermography
However, there is currently much debate about which methods should be used for screening, and how often women should be screened. At present, the most commonly recommended screening method is mammography.
What is mammography?
Mammograms are images captured with X-ray technology to look for tumors or abnormalities in the breasts.
During a mammogram, the breast is compressed between two plates and an X-ray is transmitted through the breast tissue.
The images that are captured are called mammograms.
Some breasts have dense tissue that appears white on the image film. This can mask the presence of tumors, which also appear white on film.
Other breasts are made up of low density fatty tissue, which appears grey on the image film. It is much easier to see white tumors or calcium buildups on these mammograms.
However, different groups interpret the data in different ways. Some experts say that screening provides no benefit while others say that it does.
Those who say it does estimate that over the next 10 years, for every 10,000 women who get regular mammograms, the number of women whose lives will be saved thanks to the mammogram is approximately:
- 5 out of 10,000 women aged 40 to 49 years
- 10 out of 10,000 women aged 50 to 59 years
- 42 out of 10,000 women aged 60 to 69 years
The benefit of a mammogram is greater for women in high-risk groups, such as older women, or women with a history of breast cancer in the family.
The United States Preventive Services Task Force (USPSTF) recommend that only women aged 50 to 74 years undergo a screening mammogram every 2 years. Other organizations have different recommendations, as mentioned below.
There are some potential risks that are considered to be associated with mammography and mammograms. They include the following:
- They require repeated exposure to radiation, which may cause a very small risk of cancer if used over a lifetime.
- They can lead to non-invasive cancers being diagnosed and treated when treatment is not necessarily required.
- They are not as effective for women with dense breast tissue or breast implants.
- They can lead to women choosing double mastectomies as a preventive measure.
They have a high rate of false-positive results, which can result in unnecessary biopsies and additional screening. False-positive results are those that suggest that cancer is present when it is not.
The U.S. Preventive Services Task Force recommend that women between the ages of 50 and 74 have a mammogram every 2 years.
In 2009, the USPSTF revised their 2002 suggestion of a mammogram every 1-2 years for women of 40 years and over. One of the reasons for this change was a number of studies that showed an increased risk of false-positive results when screening starts at a younger age or takes place every year.
The USPSTF now recommend that only women aged 50 to 74 years undergo a screening mammogram every 2 years. Although this advice is in line with that offered in many European countries, it differs with the recommendations of some other U.S. organizations.
The American College of Radiology and the Society of Breast Imaging both continue to recommend annual mammograms for women starting at age 40. The current guidelines issued by the American Cancer Society advise a mammogram every year for women of 45 to 54 years, and every 2 years for women of 55 years and older.
As has been shown, the heated debate concerning safe mammography policy and practice continues. In light of the debate, various emerging technologies are now being suggested as alternative options for breast cancer screening.
What is thermography?
Thermography is a test that detects and records temperature changes on the surface of the skin.
Digital infrared thermal imaging (DITI), a type of thermography used in the screening of breast cancer, uses an infrared thermal camera to take a picture of the areas of different temperature in the breasts. The camera displays these patterns as a sort of heat map.
The presence of a cancerous growth is associated with the excessive formation of blood vessels and inflammation in the breast tissue. These show up on the infrared image as areas with a higher skin temperature.
- It is a non-invasive, non-contact procedure, which does not compress the breast.
- It does not involve exposure to radiation, and so it can be used safely over time.
- It can detect vascular changes in breast tissue associated with breast cancer many years in advance of other methods of screening.
- It can be used for all women, including those with dense breast tissue and breast implants.
- Hormonal changes do not affect results.
The high false-positive and false-negative rates associated with thermography often mean that the woman will need a standard mammogram anyway.
- It has a high false-positive rate, which can result in the woman having to have the standard mammogram anyway.
- It has a high false-negative rate, which can lead to avoidance of the standard mammogram as a woman may feel she has been adequately screened.
- It is rarely covered by medical insurance.
A false-negative result is one that suggests that cancer is not present when it is. It is important to stress the high levels of false-positive and false-negative rates, as there are other screening options available.
- magnetic resonance imaging (MRI)
Ultrasonography and MRI are the recommended follow-up procedures when a woman has a positive mammogram. Ultrasonography is particularly effective for telling apart a solid mass from a fluid-filled cyst.
Small buildups of calcium are hard to see with just an ultrasound, so it is often combined with mammography for a more thorough evaluation of breast tissue.
A breast MRI uses magnetic fields to create an image of the breast. It is used to look at the size of the cancer, and look for other tumors.
Making an informed decision
Both mammography and thermography tests can suggest the presence of cancer, but only a biopsy can make a definite diagnosis. A biopsy removes a tissue sample for examination under a microscope.
To date there seems to be insufficient evidence to recommend the use of thermography alone for breast cancer screening. The American College of Radiology state that it "does not endorse thermography for detecting clinically occult breast cancer."
The U.S. Food and Drug Administration (FDA) also warn that "thermography is not a replacement for screening mammography" and continue to recommend getting a regular mammogram according to the national guidelines or as advised by a health care professional.
However, the risks of mammography should not be taken lightly, and the search for new alternative methods of screening should continue. Whatever the screening options available, women should be supported in making informed decisions about how often they want to be screened, and which screening method is right for them.