A panel of breast cancer experts offered an education session on the value of standard and genomic testing for breast cancer at the 2017 American Society of Clinical Oncology Annual Meeting (June 2-6, 2017; Chicago, IL). The session covered multiple disease states, from early-stage breast cancer to metastatic diseases, and focused on the utility of genomic and molecular information in selecting chemotherapy, endocrine therapy, and the treatment of late-stage disease.
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The session was moderated by Angela M DiMichele, MD, MSCE, Alan and Jill Miller Professor in Breast Cancer Excellence and co-leader of the breast cancer program at University of Pennsylvania (Philadelphia, PA). “The idea for this session has really evolved from the explosion of genomic information that has come out, as well as the wealth of new tools to help us understand the patient’s tumor,” Dr DiMichele said. “With those tools comes the need to understand the true utility, and how we can best use them to care for our patients and improve their outcome.”
Philippe L Bedard, MD, FRCPC, associate professor at University of Toronto and researcher at Princess Margaret Cancer Centre (Toronto, ON), spoke about the role molecular genomics can play in selecting patients for adjuvant endocrine therapy receipt. Endocrine therapy is regularly used in women with breast cancer to reduce the risk for disease recurrence and mortality, with research suggesting that adjuvant endocrine therapy can reduce mortality risk by up to 30%. Molecular testing tools have been developed to identify patients at a low risk for distant recurrence after breast cancer treatment; however, because these tools were tested in patient cohorts that included women receiving endocrine therapy or chemotherapy, it cannot offer definitive prognostic information for women not treated with endocrine therapy.
Dr Bedard offered an overview of available genomic tests, including MammaPrint, a 70-gene assay, which was tested in a cohort of patients who did not receive endocrine therapy. In MammaPrint’s validation study, approximately 96% of the cohort remained free of distant metastases after 10 years. He further referenced the Oncotype DX assay, which showed an 86% likelihood of predicting patients who would remain distant metastases free after 10 years in a validation study. “This suggests that there is a group of patients who can do well without any form of systemic therapy,” Dr Bedard said.
Despite these data, Dr Bedard concluded that the decision to prescribe adjuvant systemic therapies should be made individually and reflect the needs of specific patients, rather than rely heavily on potential genomic testing tools. “I think that the current data is insufficient to withhold any form of endocrine therapy based upon the risk identified in any of these molecular tools,” Dr Bedard said. “But I do think there is a growing body of evidence that indicates that some of these molecular tools identify low-risk patients, and as a clinician, it can provide some additional confidence in decision-making.”
Norah Lynne Henry, MD, PhD, director of breast medical oncology at Huntsman Cancer Institute (Salt Lake City, UT), discussed the integration of genomic tools into the chemotherapy decision-making process for women with early-stage breast cancer. Women with early-stage breast cancer frequently receive adjuvant chemotherapy after undergoing curative-intent surgery, in order to reduce recurrence risk. However, some women may wish to forgo chemotherapy to reduce the risk for toxicities, while others might not benefit from chemotherapy. It is important to understand which patients may or may not benefit from chemotherapy, according to Dr Henry.
“We are transitioning to an era of personalized medicine, where instead of thinking of everyone as a whole, we divide patients into subgroups based on certain factors,” Dr Henry said. “We then treat patients with specific drugs, and look at both the efficacy of treatment and the toxicity of therapy, in the hopes of maximizing efficacy while minimizing toxicity.”
The decision to prescribe or forgo chemotherapy can be made using a variety of tools, including clinical and pathologic information, as well as genomic testing. Age, comorbidity status, and patient preferences are among the primary clinical factors, and tumor size, grade, and nodal status guide the pathologic questions. Dr Henry referenced the UK-developed PREDICT website in her talk, which allows clinicians to plug clinical and pathologic factors into an assay to predict prognosis and prediction information, and includes hormone receptor status in its clinical decision-making model.
Dr Henry highlighted how genomic assays such as MammaPrint and Oncotype DX can help determine which women might benefit from adding chemotherapy to their treatment plan. However, she asserted that there are still areas regarding these tests which require further research. “These genomic assays … are very important in deciding whether or not to use chemotherapy,” Dr Henry said. “But the question that remains is how best to use these data to select specific chemotherapy regimens.”
Dr DeMichele concluded the education setting by discussing the role testing can occupy in the setting of metastatic disease. She described the understanding of the use and value in this disease setting as being in its early days, but asserted the importance of understanding how new developments will influence treatment decisions for metastatic patients in the future. According to Dr DeMichele, genomic testing may be able to help clinicians gain a better understanding of metastatic disease biology; influence the decision to treat patients with standard or specific therapies; decide whether patients are appropriate candidates for clinical trials; and aid in the monitoring of ongoing response to therapy.
“This is going to be a change in the way that we practice,” Dr DeMichele said. “Our practice setting and our resources are going to have to change, as we change the ways we treat patients with metastatic disease.”—Cameron Kelsall
For more conference coverage, click here.
