• Michael Misialek, MD

Breast Cancer Controversy: Pathologists Shedding Light

Low Grade DCIS

October is breast cancer awareness month. This year an expected 231,840 cases of invasive breast cancer will be diagnosed in women, along with 62,290 cases of non-invasive, or in-situ, breast cancer. About 1 in 8 women will develop invasive breast cancer. More than 40,000 women will die from breast cancer this year.

Types of breast cancer

Breast cancer can be broadly divided into 2 categories: invasive and in-situ. Invasive cancers are those that have broken beyond the confines of the milk ducts, and in doing so, have developed the capacity to spread to other sites (metastasize). In-situ cancers are confined to the duct system of the breast.

Breast cancer can also be subdivided into either ductal or lobular types. This distinction is made under the microscope and refers to which part of the duct system the cancer has originated from. Ductal and lobular cancers can each be in-situ or invasive.

Pathology role

Integral to breast cancer care is the pathologist. The pathologist is a key member in the care team. All treatment begins with a diagnosis and this diagnosis is made by a pathologist. Often, the pathologist is overlooked, but increasingly is now being called to the forefront. As overseers of all laboratory testing and standing at the intersection of medicine and science, pathologists are critical to value based healthcare.

DCIS controversy

DCIS can be divided into low, intermediate and high grade types based on the microscopic appearance of how much the tumor cells resemble normal cells. Surgery has been the standard of care for all types. Even after surgery a proportion will recur as either DCIS or invasive cancer. Thus far there have been no reliable tools to help determine which tumors need further treatment. As a result, many cancers are being overtreated, raising controversy on the best treatment. This was recently reflected in a Time magazine cover story. Researchers are thus taking a fresh look at treatment options.

In a recent study, researchers looked at the effects of surgery on survival for each of the grades of DCIS. They found that surgery did not significantly change survival rates for those with low grade DCIS, while surgery did have a favorable impact on survival in intermediate and high grade DCIS.

As such, there is a search for biomarkers and other predictive to tools to help determine which tumors need more aggressive treatment. This tailoring of treatment to a patient’s disease, so called precision (personalized) medicine, is revolutionizing cancer care.

Estrogen receptor (ER), progesterone receptor (PR) and HER2 are routinely measured in invasive cancers. Yet, HER2 is not routinely performed in DCIS. In a recent study of DCIS, it was found that staining for ER, PR and HER2 expression was able to predict recurrence. Tumors that were ER/PR positive, HER2 negative were less likely to recur.

These stains, performed by pathologists and visually assessed under the microscope provide strong prognostic information in breast cancer, most likely serving as surrogate markers for the genetic characteristics of the tumor. These genetic characteristics can also be determined, again by pathologists.

One such assay is Oncotype DX DCIS. A similar version of this test (Oncotype DX) has long been used in low grade invasive cancers to help predict recurrence and determine which patients should receive adjuvant chemotherapy. At last year’s San Antonio Breast Cancer Symposium, a study was presented which validated the test to predict risk of recurrence in those treated with breast conserving surgery alone. This should lead to a reduction in overtreatment of low risk patients and undertreatment of high risk patients.

Such a story is analogous to the prostate cancer debate currently underway regarding overtreatment and overdiagnosis. Indeed, there are many similarities between breast and prostate cancer.

The DCIS controversy illustrates the important role pathologists play in cancer care. All treatment begins with a diagnosis. Healing begins with a diagnosis.

Get the facts about your health. Get a copy of your pathology report. Understand it and ask questions. Discover the other member of your care team, the pathologist.

Stay tuned to Path Report during the month of October for continuing stories on breast cancer; what you need to know and how pathologists are working to make patients healthy.

#breastcancer #biopsy #pathology #precisionmedicine #DCIS

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