Breast Cancer Screening Research

All health care decisions should be made on the basis of good information. Before you undergo any health treatment, diet, or plan, make sure you have the information you need to make an informed decision that is right for you.

Another way to say this is “Check your assumptions.” What “they say” is not always true.

I can think of no better example than mammography, but before I continue, let me unequivocally state two things. First, mammography has saved many women’s lives. Second, whether or not you support mammography is up to you. Each woman should make her own choice after reviewing credible information and discussing options with her doctor. The information here is not medical advice, I am not qualified to provide medical advice, and nothing in this article should be construed as for or against any technology.

On the other hand, women should have sufficient information, rather than assumptions, when making a decision about mammograms. Breast cancer can be life-threatening and needs to be addressed seriously. Information is available if you look for it. I looked for it, and what I found troubled me.

Many organizations espouse mammograms as the best way to find early signs of breast cancer, including the American Cancer Society and the National Cancer Institute. Their websites contain a wealth of information.

How well do mammograms identify cancer?

Suspicious X-Ray image of breast

Suspicious X-Ray image of breast

The Breast Cancer Surveillance Consortium (BCSC) of the National Cancer Institute reviewed 1,838,372 screening mammograms conducted from 2004 to 2008. Their findings are available at http://1.usa.gov/1wslc4t.

The BCSC found that the overall sensitivity of mammography was 84.4%, meaning the mammograms identified 84.4% of breast cancer cases. Mammography is least effective in women under 40 because the tissue density makes interpreting the images difficult. In this age group, mammograms found 76.5% of cancer cases. Mammography is most effective in women aged 75 years and older. In this age group, mammograms found 88.5% of cancer cases.

This finding is slightly better than information from fact sheets published by the National Cancer Institute, which state, “Overall sensitivity is approximately 79% but is lower in younger women and in those with dense breast tissue.” Overall, therefore, mammograms miss approximately 21% of cancers, fewer in older women and more in younger women. Mammograms find most cases of cancer, but they miss many, too.

How often are suspicious findings actually cancer?

As it turns out, the reason why mammograms find as many cases as they do is because the technology is very poor at identifying cancer. As a result, a very high percentage of suspicious findings are sent for further analysis, whether or not they are actually cancer. With so many women being sent for additional procedures, eventually some will turn out to have cancer.

The key term here is false positive. A false positive means the mammogram image suggested the presence of cancer but a biopsy revealed no cancer. The National Cancer Institute and American Cancer Society state most biopsies for breast cancer come back negative.

According to the National Cancer Institute data, 29% of highly suspicious mammograms overall were confirmed to be malignant cancers based on biopsy results, with 9.4% for women under age 40 and 55% for women aged 80 and older. Thus, for every 100 younger women sent for biopsies because they had suspicious mammogram findings, the mammogram was wrong, and 90.6 women were subjected to invasive procedures they didn’t need. Overall, 71% of women are similarly mistreated.

This finding implies that many women without breast cancer are undergoing biopsies and treatments. If your mammograms seem positive for breast cancer, you need to find out if you actually do have cancer. In 71% of cases, though, the mammogram is a false positive.

In some cases, however, the mammogram does show cancer symptoms, as confirmed by a biopsy. But that still doesn’t mean the cancer needs to be treated!

Potentially, 54% of woman with breast cancer are overdiagnosed. The National Cancer Institute defines overdiagnosis as “diagnosis of cancers that would otherwise never have caused symptoms or death in a woman’s lifetime.” Overdiagnosis results in overtreatment. “Because doctors often cannot distinguish cancers and cases of DCIS that need to be treated from those that do not, they are all treated.” Overtreatment, in turn, “exposes women unnecessarily to the adverse effects associated with cancer therapy.”

Are mammograms safe?

Chest radiation is a risk factor for breast cancer, but the low dose of radiation from mammograms is safe relative to the risk of undiagnosed breast cancer. The radiation dose from a two-view mammogram is approximately 0.4–0.6 mSv, compared to typical annual background radiation of 3.1 mSv from natural sources.

Breast tissue is particularly sensitive to radiation, and the tissue within denser breasts, such as in younger women, is even more sensitive. Even so, the risk of acquiring cancer from a single screening is nearly non-existent, though the increased risk is life long. Each screening adds a little more risk. The National Cancer Institute notes that “Theoretically, annual mammograms in women aged 40 to 80 years may cause up to one breast cancer per 1,000 women.”

1 in 1,000 is actually a lot of women. The U.S. population of women aged 40 to 79 is 67,995,242. Approximately 67% of women in this age range get mammograms, which is 45,556,815 women. If 1 in 1,000 get breast cancer from mammograms, then mammograms may cause 45,557 cases of breast cancer.

With a 5-year breast cancer survival rate of 89.2%, 10.8% do not survive 5 years after the initial diagnosis of cancer. 10.8% of 45,557 means 4,920 women may die from breast cancer caused by mammograms. The risk is slight, but it is real.

Are there other options?

Thermographic image of confirmed breast cancer (white area)

Thermographic image of confirmed breast cancer (white area)

Given the serious nature of breast cancer, women should have some type of screening. Many women choose thermography as an alternative. The FDA has approved thermography as an adjunct (though not a replacement) to mammography.

The various health organizations that espouse mammography do not recommend thermography, noting that it is either ineffective or not sufficiently studied. They don’t cite specific studies or provide data to support this claim, so I went looking for it. I found that, actually, quite a lot of research has been done on using thermography to detect breast cancer.

How does thermography work?

Thermography provides images of heat patterns emanating from a body. This is particularly appropriate for finding cancer because “Cancerous and pre-cancerous tissues have a higher metabolic rate resulting in growth of new blood vessels supplying nutrients to the fast growing cancer cells. As a consequence, the temperature of the area surrounding the pre-cancerous and cancerous breast tissue is higher when compared to the normal breast tissue temperature” (Sree et al., 2011).

In a 1980 study of 58,000 women by Gautherie and Gros, 90% of women with suspicious thermographic findings were diagnosed with cancer. Additionally, 1,245 women with negative screenings by conventional methods had suspicious thermographic findings, and one-third of those women had biopsy-confirmed cancers within 5 years, indicating that thermography was detecting pre-cancerous conditions.

An early study by Amalric et al. of 25,000 patients found that thermography identified 91% of all cancers. More recent studies suggest that thermography finds on average 90% of cancer cases (83%–100%) and misses 9% of cancers. Parisky et al. (2003), for example, found that thermography correctly identified 97% of cancers during a 4-year clinical trial.

Thermography has been shown to identify cancers 8 to 10 years before the cancers are detectable by mammograms. Also, it poses no health risks to patients and is as effective for younger women and other women with dense breast tissue. For example, Parisky et al. found that thermography identified 100% of cancer cases in women with dense breast tissue.

How do mammograms and thermography compare?

Issue

Mammography

Thermography

Percentage of all breast cancers identified
(sensitivity; higher percentage is better)

79%
(43%–88.5%, depending on age / tissue density)

90%
(83%–100%)

Percentage of breast cancers not identified
(missed; called false negatives; lower percentage is better)

21%
(6%–46%, depending on age / tissue density)

9%

Percentage of suspicious findings that were not cancer
(called false positives; lower percentage is better)

71%–95.7%

10%–30%

Percentage / number of U.S. women who may acquire breast cancer due to the screening technology used
(lower percentage / number is better)

0.1%; 45,557

0%; 0

Which screening offers earlier detection?

 

Thermography, by 6 – 10 years

One caution about thermography

Thermography cannot be used alone if the images suggest cancer growth. Thermography doesn’t provide sufficient information about the location and size of a tumor to guide a biopsy. In most cases, an ultrasound can provide that missing information.

By using thermography to establish a baseline finding and then to monitor for changes in associated heat patterns, the development of symptoms can be tracked to indicate whether or not a woman is experiencing a real symptoms of breast cancer. If she is, the aggressiveness of the cancer can be tracked, as well, meaning whether or not the cancer is growing. Most importantly, unlike mammograms, which only look for hardened tissue, thermographic images can provide indications of risk factors that may eventually lead to breast cancer if not addressed now, thus providing a means for preventing cancer in the first place.

What should you do?

You can find research reviews and links to published studies on our website (mammography studies, thermography studies). Read the research. Talk to your doctor. Make a decision based on evidence, not assumptions.

(This article was first published in Boomers & Beyond, September 1, 2014.)

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