• Michael Misialek, MD

A Precision Medicine Approach to Breast Cancer

The precision medicine revolution has fundamentally changed cancer care. With a deeper understanding of the mutations behind cancer, and ever increasingly easier and less costly tumor sequencing methods, cancer is becoming a manageable chronic disease rather than a death sentence of the past. The contributions of pathologists have been indispensible throughout this journey. They are a crucial member of the care team. Breast cancer care is no exception.

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. Path Report, all month long, looks into the role pathologists are playing in breast cancer care.

Predicting Metastases

During the recent European Cancer Congress a study was presented looking at the genetic differences between breast cancers that return and those that do not. About one in five breast cancers, despite treatment, will recur in the original site or at a distant site (metastasis). Researchers looked at 1,000 breast cancers. Of these, 161 included recurrent tumors or metastases. They compared the cancer genetics of the primary tumors and recurrences.

It was found that there are differences in the two types of tumors, many of the changes being acquired late in the disease course. One of the important pathways involved is the JAK-STAT pathway. This is a pathway involved in cancer cell line survival and breast cancer stem cell development. Importantly, many of the genetic differences found, are actionable, meaning there is an effective treatment available targeting the particular mutation.

This important study has major implications for cancer care. Treatment must adapt and change, as a tumor evolves. We must move from a static theory of tumor genetics and treatment to that of a dynamic one, changing over time.

Early Stage Breast Cancer

Also reported at the European Cancer Congress and published online in the New England Journal of Medicine, were initial results from the “Trial Assigning IndividuaLized Options for Treatment (Rx)”, or TAILORx. In this study, 10,000 women with early stage breast cancer with low 21-gene recurrence score (Oncotype DX) results of 10 or less who received hormonal therapy alone without chemotherapy had less than a one percent chance of distant recurrence at five years. This pivotal trial demonstrates the power of precision medicine to effectively risk stratify patients with early stage breast cancer and be spared chemotherapy.

What is Oncotype DX? Oncotype DX is a test performed on breast cancer tissue that examines 21 genes associated with breast cancer. The results are reported as a score that predicts risks of recurrence, aiding in the decision of whether or not to offer adjuvant chemotherapy. Pathologists are crucial in selecting the correct tissue blocks to test. Such pre-analytic factors are of utmost importance in assuring the highest accuracy and precision of test results.

Precision Medicine Basics

Oncotype DX is just one risk stratifying test, or biomarker, that typifies the revolution that is precision medicine. Precision medicine has transformed the approach to treating cancer. In contrast to conventional chemotherapy which involves toxic drugs which kill both cancerous and normal cells, causing many side effects, precision medicine selectively targets a patient’s unique tumor characteristics.

Pathologists are involved in each step of the process. First, a tumor may be biopsied in either the operating room or radiology under CAT scan guidance. Pathologists are called upon to assess the sample, ensuring it is adequate for both diagnosis and testing for precision medicine targets (“actionable mutations”).

In the lab, pathologists examine tissues under the microscope using various stains to make a diagnosis. When appropriate, a tumor is tested for the presence of “actionable mutations”. If discovered, the patient may be eligible for targeted therapy. The success of precision medicine depends on pathologists.

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 #pathology #precisionmedicine #OncotypeDX

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