When should you screen for breast cancer?

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When should you start having mammograms to screen for breast cancer, and how often should you have them? Ask 10 doctors this question, and you might get 30 different answers. Ask a few trusted friends or relatives about their mammography schedules, and you’ll likely hear a lot of variety in their responses, too.

Why so much variation? Part of the problem is that our scientific understanding of the risks and benefits of breast cancer screening is still evolving, and the facts are open to multiple interpretations. Breast cancer experts have struggled to agree on a single set of recommendations, and unfortunately this has left many patients and doctors in a state of uncertainty about mammograms.

Explaining the USPSTF breast cancer screening guidelines

At One Medical, we study the medical literature, speak to experts, listen to what respected medical organizations have to say, and weigh the evidence carefully. One group that we pay close attention to is the US Preventive Services Task Force (USPSTF). The USPSTF is an independent group of national experts in prevention and evidence-based medicine. The members of the task force have no vested interest in whether patients get more or fewer mammograms, and they maintain a rigorous, unbiased approach to analyzing the scientific literature.

In 2009, the USPSTF published a new set of guidelines for breast cancer screening, raising the starting age from 40 to 50, and decreasing the frequency from annually to every other year. We explain these new guidelines and their rationale below, but we do not consider this set of guidelines the final word on mammograms. As with any medical decision, the decision to have a mammogram is a personal one, and one you should discuss with your primary care provider.

When and how often should I have a mammogram?

The USPSTF guideline: Women with an average risk of developing breast cancer — that is, most women — should have a screening mammogram every two years, starting at age 50 and stopping by age 75.

The rationale: Screening mammograms are very good at finding breast tumors in their early stages. But here’s a crucial point: The goal of screening isn’t to find tumors early; it’s to save lives. And for the vast majority of women, finding tumors early doesn’t save lives. Consider the following:

  • Mammograms often lead to “overdiagnosis” of abnormalities that will never cause illness or death. In particular, mammograms often detect something called ductal carcinoma in situ (DCIS), which might–but probably won’t–go on to become cancer. Most women with DCIS will not become seriously ill or die from breast cancer, even without treatment. In fact, we have no evidence that early detection or treatment of DCIS saves lives. Sadly, many women with DCIS detected by mammography end up receiving treatment, which usually includes a disfiguring lumpectomy and radiation–even though they don’t need it.
  • Mammograms also tend to give “false positive” results, causing women to undergo additional testing and even biopsies, only to discover that they have neither cancer nor DCIS. Along the way, they might endure needless radiation, disfigurement, surgical infections, and, as shown in a recent study, significant anxiety that persists for many years.
  • Some abnormalities detected by mammograms do require treatment, but finding them “early” isn’t very beneficial. Most of these cancers will respond just as successfully to treatment at a later stage–for example, when the woman feels a lump in her breast. At best, screening mammography reduces the risk of dying from breast cancer by less than 0.1 percent (or 1 patient in 1,000) over the ensuing 10 years.
  • Sadly, a tiny percentage of breast cancers — the most aggressive, deadliest cancers — will progress to cause serious illness and death despite early detection and treatment. Mammograms are of no benefit in these cases.

Taking all this information and much more into account, the USPSTF concluded that starting screening at age 50 and increasing the interval between mammograms from one year to two years has virtually no effect on the detection of clinically important breast cancers, but dramatically decreases the risk of subjecting women to incorrect diagnoses and unnecessary treatments.

What if I have a family history of breast cancer?

The USPSTF guideline: Women with a family history of breast cancer or ovarian cancer — or who are concerned that they are at increased risk of breast cancer — should discuss their history with their primary care provider to determine the best plan going forward.

Assessing your risk: If you have a family member with breast or ovarian cancer, your primary care provider can assess if you are at increased risk. The extent of your risk will depend upon which family members have been affected, and your ethnic heritage. Women who had radiation therapy to the chest for a childhood cancer like Hodgkin’s lymphoma are also at increased risk. If your primary care provider has determined you are at increased risk, you’ll want to discuss the next steps you should take, which could include mammography and/or genetic testing.

I’ve heard MRIs are more sensitive at detecting breast cancer. Should I get one?

The USPSTF guideline: There is no evidence supporting the use of MRIs of the breast as a substitute for routine film mammography.

The rationale: MRIs haven’t been shown to reduce breast cancer mortality, and they may increase the risk of false positives and unnecessary procedures.

One exception may be their use in women with dense breast tissue, in which MRIs are a little better than film mammography at detecting cancer in high-risk people. But this still raises the question of overdiagnosis — that is, false positives and detection of lesions that may never cause harm. These tests are also expensive. For all these reasons, MRIs aren’t used to screen women at average risk.

What does this mean for me if I’m at average risk of breast cancer?

For women at average risk, the evidence supports a reasonable middle ground of screening for breast cancer by undergoing mammograms every two years, starting at age 50 and stopping by age 75. However, we understand that this is a very personal decision. Your primary care provider can help you assess your individual risk for breast cancer, discuss the pros and cons of different screening approaches, and help determine the best strategy for you.

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The One Medical blog is published by One Medical, an innovative primary care practice with offices in Boston, Chicago, Los Angeles, New York, Phoenix, the San Francisco Bay Area, Seattle, and Washington, DC.

Any general advice posted on our blog, website, or app is for informational purposes only and is not intended to replace or substitute for any medical or other advice. The One Medical Group entities and 1Life Healthcare, Inc. make no representations or warranties and expressly disclaim any and all liability concerning any treatment, action by, or effect on any person following the general information offered or provided within or through the blog, website, or app. If you have specific concerns or a situation arises in which you require medical advice, you should consult with an appropriately trained and qualified medical services provider.

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