Genetics and Genomics: What is the Difference?

One of the primary goals of cancer care is to prescribe personalized recommendations for each patient. This requires a thorough understanding of the patient’s risk factors for development of cancer (genetics) as well as an in-depth analysis of the tumor to be treated (genomics). When the clinician is able to differentiate the specific genetic and genomic profiles of a patient and tumor, the treatment and surveillance plans can be individually tailored, resulting in optimal care.

Genetics is the study of heredity (how traits are passed down through generations.) In the context of breast cancer risk assessment, a genetic test refers to analysis of specific genes known to be associated with cancer risk, referred to hereditary predisposition genes. Each cell contains two complete sets of DNA (genes), one set was inherited from the mother and the other from the father. Most of the cancer syndromes related to breast cancer risk result from a single defective copy of a specific gene. A common misconception is that breast cancer risk is only inherited from the patient’s mother, but actually, an altered gene from either parent confers the same degree of risk. A physician or genetic counselor obtains a detailed family history and can often find evidence of the genetic mutation throughout several generations. A patient who is found to carry a mutation known to be associated with increased cancer risk is counseled on management and/or surveillance strategies aimed at either reducing the risk for cancer development or increasing the likelihood of early detection.

Breast cancer genomics is the study of the genes within a tumor. The genomic profile of a tumor is very helpful in understanding the specific characteristics of a tumor, such as aggressiveness, likelihood of spreading beyond the breast, recurrence risk, and prediction about degree of benefit from chemotherapy. Multiple genes are analyzed in the laboratory to determine which genes are more active, which are less active and which are altered within the tumor. Genomic analysis adds such valuable information about the tumor that will be incorporated into the standardized staging of tumors as of 2018.