 |
| Dr. Lauren Schnaper |
The first mammograms were performed in Europe, as early as 1913. They were not the high tech digital films we know today and did not catch on for many decades because surgeons treated all breast tumors, no matter the size or the behavior, with radical surgery. Finding smaller tumors that might be treated with more limited procedures was a concept foreign to physicians. They believed, erroneously, that removal of as much tissue as possible was the only way of keeping breast cancer from “coming back.” That is a tenacious concept, still believed by many people.
By the early 1960s, when surgeons began to question radical mastectomy dogma, mammography was resurrected and the first screening trials began. Screening mammography was not widely performed until the 1980s.
The definition of a screening test for a population or an individual means that they are asymptomatic (no lumps or bumps, skin changes, nipple abnormality, etc). The screening criteria also may not apply to individuals who are considered to be at high risk (strong family history or genetic mutation carrier, previous breast cancer). The benefits (reduction in the risk of dying from breast cancer) must be weighed against the financial and non-financial costs (radiation exposure, additional tests and biopsies, anxiety, money per test).
There are two major problems with screening: Underdiagnosis means that the mammogram failed to find a cancer that will eventually be discovered when it becomes a lump or presents with some other symptom. Overdiagnosis means: (1) that an abnormality is found that is not a cancer but is evaluated with multiple procedures as if it was a cancer or (2) a true cancer is found but one that would never become clinically significant during the indivdual’s life-time and would not influence how they are treated, how they live or die.
In America, we have trouble with the concept of costs vs. benefit. We believe that if a million women need to be screened to save one life, then so be it. We picture ourselves or our loved ones as that one life saved.
The non-financial costs of screening are influenced by several biases:
Lead time bias means two women develop a deadly breast cancer on the same day. They die of that cancer on exactly the same day, five years after diagnosis. They both have treatment but no treatment that they receive will change the behavior of their cancers or save their lives but they are not aware of that fact. The first woman’s cancer is picked up on a mammogram in year #1 after the cancer is born. She and her family believe that mammography has benefited her because she has had four additional years of life following her diagnosis. The second woman never had a mammogram. Her cancer is picked up as a lump in year #4. Her survival appears to be shorter than that of the first woman, even though it is identical to the first woman’s. To be effective, screening must decrease mortality from the disease, not just give the appearance of doing so.Length time bias speaks also to the variable behavior of cancer. More poorly behaved fast growing tumors do not lend themselves to screening as they often occur in between the screening test interval and have already spread before they are detectable. Slow growing tumors are amenable to screening because they might hang around for a long time before doing any damage.
The concept of “early detection” is a simplistic view of a disease that has numerous and complex behaviors; no two cancers are the same. In the extreme, a few are deadly from the day they are born but most require treatment and are ultimately curable.
Herein lies the controversy that waxes and wanes in the popular press. Who should be screened and how often? The United States Preventive Services Task Force (USPSTF) has reviewed screening mammography studies in 2002 and 2009. The members took many factors into account. In 2002, they recommended that the screening interval be changed to one to two years. In 2009, they changed their recommendation to every two years because they saw the same decrease in the death rate in the annually screened groups as in the longer screening interval groups. They also found that there was no difference in the chances of detecting an aggressive cancer between the one year and the two year screening interval.
The risk of developing breast cancer increases with age. The “readability” of mammograms gets better after menopause when breast tissue goes away and is replaced by fat. The average age of menopause in America is 52. The behavior of breast cancer is also less aggressive in older women. The USPSTF recommend screening every two years between 50 and 74 and individualized screening for women over 74.
In women who are still menstruating, there is a lot of breast tissue which is referred to as “breast density” on mammogram – as if this is an abnormality or a disease. It is not. The breast is a round object, compressed by the mammogram plate to be a flat picture. The overlapping shadows of the tissue are white on the film. Because all of the abnormalities – good or bad – are also white, they may not be seen if transposed on a white background. Digital mammography has more contrast and is more sensitive to changes in mammograms of menstruating women or those on exogenous hormone therapy. Again, the USPSTF recommends individualized screening decisions for women in their forties but at a two year, rather than a one year, interval.
It should be noted that the American College of Radiology, the National Comprehensive Cancer Network, and the American Cancer Society continue to recommend annual screening for all women over 40. They do not offer an opinion as to at what age mammography screening should stop.
The National Cancer Institute advises screening every one to two years beginning at age 40. The American College of Physicians, every one to two years age 50-74 with individualized recommendations ages 40-49. The American College of Ob/Gyn recommends every one to two years from 40-49 and annually thereafter, with no stopping recommendation.
Interestingly, the United Kingdom National Health Service recommends screening every three years from age 47-73.
NO organization recommends a baseline mammogram at age 35.
In order for a screening test to be adopted or changed it must improve on all of the parameters already discussed. Touted as the new era in breast imaging is Tomosynthesis or 3D Mammography. It is a digital mammogram, that instead of taking a flat top-to-bottom and side-to-side picture, the machine swings around the breast, taking as many as 60 thin “slices” through the tissue. This may benefit women with dense breasts on imaging as it does away with overlapping tissue shadows so that white lesions can be separated from the white tissue background. Another advantage is that there will be fewer call-backs for additional films to evaluate vague areas of density.
Although some say there is less pain during a 3D mammogram, this is not true. Compression is the same. Other disadvantages: Although 3D mammography has FDA approval, there may be additional out-of-pocket expense to the patient because there is no insurance reimbursement at this time. There is increased radiation exposure, approximately that of the old analog films, because both 2D and 3D mammograms are performed at the screening visit. The 2D films will probably not be needed after the technology for creating a 2D picture out of the 3D slices is improved. Radiologists have to be trained in new reading techniques and interpreting the films takes about twice as long as for the 2D films alone. In terms of increasing ability to detect cancer or decreasing mortality from breast cancer, studies are underway.
**********
I thank Dr. Schnaper for her insights and continued work on behalf of all the patients who turn to GBMC for superior breast care.
For anyone who isn’t familiar with GBMC’s program, the Comprehensive Breast Care Program and its affiliated Advanced Radiology Breast Imaging Center have received national accreditation as Centers of Excellence, which speaks to the integrated and superior care our patients receive. From the Breast Cancer Risk Assessment Program to GBMC’s Rapid Diagnostics Program, our patients truly benefit from the expertise of our physicians and care providers and the advanced technology available for diagnosis and treatment of breast cancer. But, most importantly, our team of specialists takes to heart GBMC’s vision of treating every patient, every time, the way they would want their own loved ones to be treated.
Finally, GBMC is currently offering 3D Tomosynthesis Mammography at the Breast Care Center. You can call 443-279-9639 for more information or to make an appointment or visit the Comprehensive Breast Care Center page on GBMC’s website to learn more.
Very explicit,concise information.I really like the simplicity of the presentation and above all it cleared up multiple questions flowing through my mind since my first mammogram that l just had.Thanks Dr.Chessare and Dr.Schanaper.
ReplyDelete