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Genomic Tests Help Breast Cancer Patients

Oct 06, 2016 11:23AM ● By Becky Coburn

By Christine Chung, MD


Jane is a 60 year-old grandmother who found out she has breast cancer. She had a lumpectomy of the right breast, and the breast tumor was removed.  She is worried because the surgery showed a 2 centimeter invasive ductal carcinoma.  After dealing with the stress of the diagnosis and surgery, and now confronted with a recommendation to do begin chemotherapy, she asked, “Doctor, do I really need to have chemo?”

Oncologists consider various clinical factors before recommending chemotherapy for a patient.  These include the patient’s age, tumor size, grade of the tumor (tumors are graded based on how aggressive the cells appear under the microscope), and number of lymph nodes containing cancer cells at the time of diagnosis. The expression of various receptors on the tumor cells – the estrogen receptor, progesterone receptor, and her2 neu receptor also help identify high-risk patients who would benefit from chemotherapy. 

But the analysis doesn’t stop with the clinical diagnosis; in our arsenal of diagnostic tools, we also have genomic assays that can help assess if a patient may benefit from chemotherapy. These genomic assays test a piece of the patient’s breast tumor to see which genes are turned on in the cancer cells.  The expression of these genes is used to estimate the likelihood of breast cancer recurrence elsewhere in the body.  These genomic tests, known commercially as Oncotype Dx, Mammaprint, or PAM 50, can further guide oncologists in giving chemotherapy recommendations.

How much weight should a doctor place on a genetic test, particularly when it conflicts with the clinical diagnosis?  A recent study in the New England Journal of Medicine (Cardoso et al) identified 1550 breast cancer patients with high-risk clinical features for whom chemotherapy would normally be recommended. However, the genomic test classified these same patients as low risk.  These “clinical high risk/genomic low risk” patients were then randomly assigned to receive chemotherapy.  After five years, 96% of patients who received chemotherapy were alive and cancer-free, while 94.4% of patients who avoided chemotherapy were free of disease.  Thus, the survival was similar among patients classified by the genomic test as low risk, regardless of whether they received chemotherapy.

Dr. Tiffany Svahn, a breast cancer specialist at Diablo Valley Oncology, says the “genomic evaluation of breast tumors prevents us from over-treating many patients, which is what we did before we had genomic testing. These assays have benefitted so many women diagnosed with early stage breast cancer.”

Creating a cancer therapy plan is a complicated and nuanced process, requiring a thorough discussion with your oncologist about clinical, genetic, lifestyle, and other factors.  These genomic tests are an important addition in the decision-making process, though the chemotherapy decision remains a complex one.

Christine Chung, MD, is a board certified radiation oncologist with Diablo Valley Oncology & Hematology Medical Group and practices in Pleasant Hill and Berkeley. For more information, please call 925-677-5041 or visit