Breast Cancer Screening – What’s Behind the Guidelines?

Last week, the US Preventive Services Task Force (USPSTF) released updated recommendations for breast cancer screening. In the name of being more transparent, there is time now for the public to comment. I thought I’d take this opportunity to point out the difficulties encountered in formulating these guidelines, and making it clear who they apply to and why.  

SCREENING SCHEDULE:

First off, they studied only those from 40 to 75 years old with no symptoms, and no preexisting breast cancer (invasive or non-invasive), no genetic mutation, and no prior chest radiation. Anyone who is at higher risk for breast cancer should discuss screening with their physician, and would likely be on a different schedule. For the general population, the Task Force has not changed its 2009 guidelines that recommend a mammo every 2 years for ages 50-74. For those 40 – 50 years old without any high risk factors, patients can either do mammos or not, depending on their comfort level.

If you are aware of a different schedule, it may be because current guidelines from the American Congress of Obstetrics and Gynecology (ACOG) and the American College of Radiology (ACR) are different, recommending annual mammos for all women 40 and over, without an upper age limit.

MAMMOGRAPHY TECHNOLOGY:

In order to be reporting about how mammography has affected the diagnosis and risk of death from breast cancer over the past several decades, the Task Force necessarily looked at data starting from 20-30 years ago. Really, nothing in the field is the same now as it was 30 years ago. We know that detection has improved, but so has treatment, so maybe early detection isn’t as crucial as it was years ago? The Task Force commissioned researchers from Georgetown Comprehensive Cancer Center to conduct modeling studies that account for the new technology and new treatment options. This allowed the Task Force to weigh results from clinical trials as well as results from modeling a cohort of women, using the most recent cancer registry data. It’s tricky business assessing how the new techniques will affect outcomes.

Further, the info given states that one in 5 women diagnosed by screening mammos probably would not have any ill health effects if they remained undiagosed and untreated. Unfortunately, at this point, we can’t predict whose lesions need to be treated and whose need not. And once detected, who would be willing to sit tight and NOT take care of a lesion that MOST LIKELY won’t progress?

Regarding recent advances in screening, although the 3D mammos are promising, there is not yet enough evidence to favor its use regarding improved health, quality of life, or fewer deaths among those screened. 3D mammos at this time often require doing 2D as well, which would involve double the radiation. In some cases now, and hopefully moreso in the future, they should be able to reconstruct the 2D from the 3D, thereby limiting the radiation exposure. Current research studies on 3D mammography did not show any improvement in long-term health outcomes; research is ongoing.

Those with dense breasts do have an increased risk of breast cancer and there is a decreased ability of the mammography to detect it. However, one in five mammos may be read as dense by one radiologist and not dense by another. Furthermore, It is unclear that ultrasound or MRI would be beneficial as part of the screening process in this population. At this time, they are not currently recommended by the Task Force across the board, but can be used as needed, while more research is done.

RISK-BENEFIT RATIO:

Any screening test – i.e., a test that looks for a finding in people without symptoms – that is used on a large population must be carefully evaluated. Since the COST is high, we need to be sure the BENEFIT makes it worthwhile. In this instance, on the cost side is the financial cost of screening, the false positives that require further testing (that might incur out-of-pocket costs) to make sure all is well, the false negatives that erroneously assure us that all is well, the risk of radiation exposure, and the discomfort of having the test done.

Included as a cost, the Task Force’s data show that the lifetime risk of breast cancer attributable to the radiation from the mammos themselves is 27 per 100,000 screened, leading to 5 deaths (but preventing other deaths from breast cancer). That risk increases in women with large breasts who often require additional views.

The benefits, on the other hand, include peace of mind that another check is normal, and early detection of breast cancer which thereby allows for curative treatment.

The Task Force has determined that mammography from age 50 to 74 decreases the risk of dying from breast cancer, with the best risk-to-benefit ratio attained with testing every 2 years instead of every year. This is based on modeling of the natural history of invasive and non-invasive breast cancer, and finding that the additional BENEFIT of yearly screening is LESS THAN the additional RISKS of radiation and false positives as noted above.

The risk-benefit ratio also is not as good in those under 50 – so testing in the 40-50 age range should be a personal decision based on ‘values, preferences and health history’. Those with a first-degree relative (mother, sister, daughter) with breast cancer, for instance, would benefit from this earlier screening.

The ‘risk’ in this younger age group is that the false positive rate is higher — 12% versus 7% in the 70-74 year old population — meaning more biopsies and other workup will be done when there is actually no disease. Also, the earlier screening is started, the greater the cumulative radiation dose. Testing under 50 years old is given a “C” recommendation by the Task Force — that the balance of benefits and harms is close. The net benefit is small, so the decision should be based on the individual situation. This differs from the recommendations of the radiologists and Ob/Gyns, as noted above, for yearly mammos starting at age 40. Interestingly, the United Kingdom has for years recommended mammography screening every 3 years for women age 50-70.

For those over 75, the Task Force makes no recommendation for screening because women in this age group have been excluded from trials they studied, so no good data is available. However, guidelines from the other groups don’t set an upper age limit.

In all of this, there is room for discussion with your physician.  Using the guidelines as an outline, if you are radiation-phobic like me, you might opt for less frequent screening.  If you feel uneasy with the thought of missing any possible growth, then you would opt for the most frequent screening advised.  I hope this information serves as the basis for a well-informed discussion.  

STILL INTERESTED:

More information from the Task Force, radiologists and Ob/Gyns can be found at the links below. Just so you don’t think I only take care of women, I will write about PSA screening soon. Many of the issues are comparable, regarding issues of chasing false positives and using strong therapies with side effects to treat lesions that may never end up causing problems.

For more information from the Task Force about breast cancer screening, see:
http://screeningforbreastcancer.org – video and opportunity to comment on the guidelines.
http://screeningforbreastcancer.org/frequently-asked-questions
http://screeningforbreastcancer.org/assets/content/AHRQ_MythFacts-Breast_Cancer_Screening-1pg-Rnd05A_%281%29.pdf

For the perspective from the American College of Radiology:
http://www.acr.org/~/media/ACR/Documents/AppCriteria/Diagnostic/BreastCancerScreening.pdf

And from ACOG for the Ob/Gyns:
http://www.acog.org/Patients/FAQs/Breast-Screening-Mammography-and-Breast-Self-Awareness