Posts

20 July 2015

This is not a new question, and I promise there will be many parts to this story. The latest: Breast Cancer Screening, Incidence and Mortality Across US Counties, published in the July 2015 issue of JAMA Internal Medicine. The authors of the study noted that rates of early breast cancer detection have increased with the widespread use of screening mammography, but death rates from breast cancer have not decreased, leading to the conclusion that many breast cancers are “overdiagnosed”.

One would expect that if there were an increase in the number of early breast cancers detected due to screening mammography, fewer women would subsequently die from breast cancer. Isn’t early detection the key to survival? A reasonable question that is raised from this study is “What is the value of screening mammography?”. First, several points:

  1. The authors noted that the rates of early breast cancer, especially DCIS, have increased significantly with the widespread use of screening mammography.
  2. It is well known that some breast cancers have such an indolent biologic behavior that they will never become a threat to a breast or to a life.
  3. The more we screen, the more we find. Not everything needs to be found.
  4. Finding indolent lesions is considered “overdiagnosis”. Treating these lesions with traditional surgery, radiation and other treatments is considered “overtreatment”.
  5. Early detection does not always equal cure. Some breast cancers have a very aggressive behavior, and may prove to be fatal even when diagnosed in early stages.

Before you cancel your upcoming mammogram, appointment, some limitations of the study were pointed out in an accompanying editorial: Effect of Screening Mammography on Cancer Incidence and Mortality. One of the biggest criticisms is how the study was actually conducted, using the “ecological method”, which studies large groups, not individuals. It is not possible to tell if the women who were diagnosed with breast cancer are the same ones that subsequently died due to the disease. Other limitations of this of study are that no information is available on tumor subtypes or adjuvant therapy (chemotherapy, hormonal therapy and radiation). Another limitation of the study is that it evaluated data over a 10 year period, which might not be long enough to have an impact on survival rates. Finally, it was discussed that there was the potential for “confounding bias” – factors associated with an increased risk of breast cancer might also be associated with an increased rate of obtaining screening mammograms. [For a good discussion of the types of bias that may be present in research studies, review this article from HealthKnowledge.]

There is no question that we are finding more early stage breast cancers, including DCIS. There is much debate on whether or not DCIS even represents “cancer”. But the reality is that while we recognize that not all cancers will progress, we do not yet have the ability to predict the behavior of a cancer with certainty for an individual woman. We do not yet have that crystal ball.

So now what? The conclusion always seems to be “ask your doctor”. But physicians do not have all of the answers. What is clear is that the decision to begin or continue screening mammography is no longer automatic – discussion about the benefits of mammography, the potential harms, a woman’s own risk tolerance, and personal beliefs is necessary – this is the essence of shared decision making.

Various online tools have been developed to help women make more informed decisions. One is Weill Cornell Medical College’s Breast Screening Decisions, meant to be used by women in their 40’s. This is a start. We also need to develop that “cancer crystal ball”, which will allow us to more accurately predict who will develop cancer, and the behavior of a cancer that has developed. We’re just not there yet. Stay tuned as this is certainly not the last word on this issue.

3 August 2013

What’s in a name? In the case of cancer, there are myths, fears, and misinformation – more than perhaps any other illness.

Cancer encompasses hundreds of different diseases and each one is complex. Even women diagnosed with exactly the same “type” of breast cancer and who undergo the same treatment can have very different outcomes. Not all cancers are equal and not all cancers are lethal.

While early detection and treatment were once equated with improved survival, we now know that tumor biology (characteristics governing the behavior of spread and response to treatment) plays an extremely important role in the prognosis of an individual cancer. There is an increasing recognition that current screening tests, meant to diagnose cancer in the earliest stages, will often diagnose lesions that have minimal potential to become aggressive or lethal. As our screening technology improves, we are detecting more patients in early stages or with pre-cancerous conditions and we are treating those patients with surgery and other potentially toxic therapies.

In 2012, the National Cancer Institute convened a working group to “evaluate the problem of ‘overdiagnosis’ which occurs when tumors are detected that, if left unattended, would not become clinically apparent or cause death.” Unrecognized overdiagnosis, they stated, “generally leads to overtreatment”1.

The recommendations of this panel were recently published in the Journal of the American Medical Association: Overdiagnosis and Overtreatment in Cancer, An Opportunity for Improvement.  The authors provide five recommendations:
1. Physicians and patients alike need to acknowledge that screening results in overdiagnosis – especially in breast, lung, prostate and thyroid tumors.
2.  The term ‘cancer’ should be reserved for describing lesions with a reasonable likelihood of lethal progression if left untreated.
3.  Create observational registries for low malignant potential lesions in order to better understand prognosis and best treatment options.
4. Mitigate overdiagnosis with an ultimate goal of preferential detection of consequential cancer while avoiding detection of inconsequential disease.
5. Expand the concept of how to approach cancer progression by controlling the environment in which cancerous conditions arise.

While these are certainly laudable goals, some important points should be made, especially in regards to breast cancer and ductal carcinoma in-situ – the most important being that we do not currently have biomarkers or other indicators that can clearly distinguish a potentially lethal cancer from a more indolent one. The field of cancer genomics is rapidly changing, and today more than ever, we can obtain very sophisticated prognostic information regarding an individual’s tumor. Despite that, Dr. Larry Norton, medical director of the Evelyn H. Lauder Breast Center at Memorial Sloan Kettering Cancer Center, stated “Which cases of DCIS will turn into an aggressive cancer and which one’s won’t? I wish I knew that. We don’t have very accurate ways of looking at tissue and looking at tumors under the microscope and knowing with great certainty that it is a slow-growing cancer”2.

Regarding the modern management of DCIS, there are three points to remember:
1. When DCIS lesions diagnosed by needle core biopsy are surgically removed (which involves removal of substantially more tissue from the abnormal area), there is an approximately 15% rate of ‘upstaging’ to invasive ductal cancer 3. Put another way, one cannot always reliably predict the behavior of an entire lesion based on a core biopsy specimen.
2. During surgery for DCIS, axillary lymph node metastases have been demonstrated up to 20% of the time, usually indicating missed microinvasion or invasion 4.
3. Finally, if DCIS recurs, 50% of the time it is invasive 5.

What is important to be aware of is that any woman with breast disease, including DCIS, should be presented with the information necessary so that she may gain an understanding of where her diagnosis stands in the biological spectrum and the wide array of choices she has for treatment. DCIS is far from simple, and it is not to be taken lightly. Clearly there are cases where ‘watchful waiting’ is safe – but we cannot always reliably predict who will truly benefit from treatment. Moving forward, we need to be aware of the facts – what medical technology can provide the patient and the physician now, and we need to ask how we can drive this conversation in the future.

Deanna J. Attai, MD, FACS
Michael S. Cowher, MD