New Assay Determines Risk of Recurrence for Breast Cancer Patients

Image courtesy of Shutterstock

For women with hormone receptor-positive breast cancer, the decision to undergo adjuvant chemotherapy following endocrine therapy has important implications to health and well-being. Now, a gene signature assay may help clinicians make more precise recommendations and there are new guidelines to reflect that.

St. Gallen International Breast Cancer Guidelines have been updated to include the PAM50 gene signature for the first time. The PAM50 (Prosigna) Breast Cancer Prognostic Gene Signature Assay estimates risk of recurrence during the first 5 years and beyond, following diagnosis. Prosigna can identify whether postmenopausal women with node-negative (stage I or II) or node-positive (stage II) will need adjuvant chemotherapy. At a time when personalized medicine has become more precise and the risk of over treatment to the patient can have life-long side effects, this new diagnostic tool may prove to be very useful.

Charles Perou, PhD, professor of genetics and pathology, and colleagues at the University of North Carolina Lineberger Comprehensive Cancer Center in Chapel Hill, first discovered the PAM50 gene signature. The Prosigna assay uses gene expression with clinical variables to develop a risk category and score (by number) to access a patient's risk of recurrence. This assay measures gene expression levels of RNA extracted from formalin-fixed, paraffin-embedded tumor tissue previously diagnosed in patients with invasive breast carcinoma. The test categorizes breast tumors into one of four main subtypes by looking at the expression of 50 genes. The four types are luminal A, luminal B, HER2-enriched, and basal-like.

The announcement that the breast cancer guidelines have been updated with this new diagnostic tool was announced during the recent St. Gallen International Breast Cancer Conference, an annual event which took place in Vienna, Austria, March 18-21, 2015. This event includes experts in cooperative groups and cancer treatment centers worldwide. To develop the consensus guideline, a panel of 48 experts responded to 200 questions about breast cancer research and current treatment plans.

Some organizations are becoming early adopters, including the German Association of Gynecological Oncology (AGO) who viewed this as a precise prognostic assay. The AGO guidelines note that genomic tests should be used to select patients when clinical pathologic features alone do not provide enough evidence to make a clear decision about therapy. In the United States, the Prosigna assay is available for diagnostic use when ordered by a physician.  

References:

• Coates AS, Winer EP, Goldhirsch A, et al. (2015). Tailoring therapies - improving the management of early breast cancer: St GallenInternational Expert Consensus on the Primary Therapy of Early Breast Cancer 2015. Annals of Oncology.
• Globe Newswire. (2015). St. Gallen International Breast Cancer Guidelines Recognize Power of Prosigna/PAM50 to Inform Treatment Decisions and Spare Low Risk Breast Cancer Patients Unnecessary Chemotherapy.