By Kelliann Fee-Schroeder, RN, OCN®, and Elisabeth King, RN, FNP, AOCNP®, AGN
Genetics versus genomics: Is there a difference? Does it even matter? There is, and it does. In our era of precision medicine, also referred to as individualized or genomic medicine, being able to differentiate the terms is a first step in establishing a foundational understanding of what they mean for cancer care from prevention to treatment.
According the National Human Genome Research Institute (NHGRI), genetics is the study of individual genes, whereas genomics is the study of the entire genome, or all of an organism’s genes, interactions among genes, and the environment’s role in affecting them.
The terms are particularly important in oncology because cancer is caused by pathogenic variants (mutations), or harmful changes in certain genes. This can result in uncontrolled cell growth or make cells unable to repair themselves, thus leading to the development of cancer.
The hereditary or inherited variants in specific genes that can be passed on from generation to generation and significantly increase a person’s chance of developing cancer are considered cancer genetics. More than 50 hereditary cancer syndromes have been identified, caused by pathogenic variants in specific genes that predispose individuals to developing certain cancers.
An estimated 5%–10% of all cancers result from inherited genetic pathogenic variants. Some examples of hereditary cancer syndromes, related genes (which may have pathogenic variants), and types of cancers include:
- Hereditary breast and ovarian cancer syndrome (BRCA1, BRCA2, PALB2): breast cancer, ovarian cancer, prostate cancer, pancreatic cancer, and melanoma
- Lynch syndrome (MLH1, MSH2, MSH6, PMS2, EPCAM): colorectal, endometrial, stomach, breast, ovarian, small bowel, pancreatic, prostate, urinary tract, liver, kidney, and bile duct cancers
However, as technologies and our knowledge have improved, cancer has moved beyond the landscape of just “single gene, single cancer risk” and now encompasses the larger application of genomics. The concept broadens the study of cancer to include not just a person’s individual genes but also how different genes interact with each other and the environment and identification of possible therapies and new diagnostic methods.
To make understanding even more challenging, in addition to the genome a person is born with (germline), tumors themselves have their own unique genomic makeup (somatic). In some cases, identifying their genomic variability may help determine which cancer therapies to recommend.
Evaluation of the tumor genome’s somatic changes for consideration of targeted therapies is often standard of care. For example, KRAS mutations in metastatic colon cancer confer resistance to cetixumab, so the treatment is only offered to patients who have KRAS wild-type (KRAS-mutation negative) colon cancer tumors. PARP-inhibitors are indicated for patients with ovarian cancer who have certain genomic alterations, including BRCA1/2.
Although genetics and genomics may seem intimidating and overwhelming to both new and experienced oncology nurses, understanding the terms and how they apply to cancer and cancer care is a first step toward incorporating this growing and changing field into professional oncology nursing practice.
As our understanding of how a person’s genetics and genomics influence cancer prevention, diagnosis, prognosis, and treatment options increases, oncology nurses will need to deepen their understanding of genomics, applications in practice, and how best to support patients and families.