Key Definitions
Genomics: the study of a person’s total genetic code
Medical genetics: the study of how individual genes can be identified and used for medical applications such as targeted drug therapies, risk for or diagnosis of disease, and tailoring treatments
Personalized medicine: the study of patients’ unique environmental influences as well as the totality of their genetic code to tailor personalized risk assessments, diagnoses, prognoses, and treatments
Pharmacogenomics: the study of how patients’ genomes affect responses to medications
Since the Human Genome Project map was completed in 2003, medical genetics has become an increasing field of study, filled with rapid discoveries. Thanks to the concepts of inheritance, genetics, and medical genetics, researchers have found that many factors other than the presence or absence of a single gene predict disease. The fields of genomics, pharmacogenomics, and personalized medicine are helping scientists and healthcare providers better study and treat genetic diseases such as cancer.
In his article in the August 2014 issue of the Clinical Journal of Oncology Nursing, Andrew Blix gave an overview of personalized medicine, genomics, and pharmacogenomics and how they relate to oncology. He also explained key considerations for oncology nurses and why they need a basic understanding of this area to provide the best care to today’s patients with cancer.
Overview of Oncology Genetics
The cells in the human body are in a constant cycle of growth and division. However, sometimes during that normal process, abnormal changes are introduced in the form of DNA mutations. Most cancer mutations involve oncogenes and tumor suppressor genes.
- Oncogenes: These genes function to regulate cell growth but can mutate to instead enable abnormal cell growth. An example of an oncogene mutation is the RAS mutation that is present in about one-third of all tumors, including lung, colon, and pancreatic cancer.
- Tumor suppressor genes: These genes normally turn off abnormal cell growth, repair damaged DNA, or cause cells to die. BRCA1 and BRCA2 are examples of tumor suppressor genes.
Additionally, cancer mutations are classified as either germline or somatic.
- Germline mutations: Comprising only 5%–10% of all cancers, these mutations are inherited. BRCA1 and BRCA2 are also examples of germline mutations, causing hereditary breast and ovarian cancers.
- Somatic mutations: Much more common are somatic mutations, which develop over a patient’s lifetime in response to various external factors (e.g., radiation, toxins, viruses). The majority of individual somatic mutations do not result in cancer; rather, cancers develop when several types of somatic mutations accumulate over time.
In fact, Blix cited studies that show that four to seven specific mutations are usually necessary for cancer to develop. And the study of genomics has shown that many of these specific mutations are tied to certain cancers, such as the Philadelphia chromosome to chronic myeloid leukemia. With this knowledge, personalized medicine can be developed to target these specific genetic mutations. Imatinib mesylate was one such treatment created to target the Philadelphia chromosome and treat CML.
“By analyzing patients’ DNA for specific genes (genetics) and for certain genes in combination with certain expression (genomics), healthcare providers can identify the risks for developing disease, diagnose specific diseases, offer more accurate prognoses, tailor individualized treatment plans, and prescribe targeted drugs. This is the future of personalized medicine in oncology,” Blix explained.
How Genetics, Genomics, and Personalized Medicine Are Used in Oncology
One of the more well-known ways researchers and healthcare providers are using this science is for genetic risk assessment for cancer. Risk assessments take many genetic factors into consideration and can estimate an individual’s risk for cancer based on family history. Familial risk factors include
- Early onset of cancer in a family member (e.g., breast cancer before age 45, colorectal cancer before age 50)
- Individual family members having multiple, different primary cancers
- Cancer in multiple generations of a family
- Certain cancers occurring together (e.g., breast and ovarian cancer, pancreatic cancer and melanoma)
Genomics, on the other hand, is increasingly used to achieve a more detailed diagnosis. Whole-genome sequencing of an individual’s cancer allows clinicians to diagnose specific subtypes that may respond to certain targeted therapies. “As genome sequencing becomes faster and more accurate, cancer genome sequencing will become more prevalent in clinical diagnostic use,” Blix wrote.
Together, genetic and genomic testing can also help clinicians determine cancer prognosis and treatment. Genomics can predict disease severity and outcomes in cancers such as breast and lymphomas, and it also helps clinicians anticipate individual patient variations in drug metabolism, such as with the P450 family. Overexpression of P450 enzymes causes patients to break down certain cancer treatments, so healthcare providers can compensate by prescribing effective drugs at the best doses. Genetic testing can also help clinicians anticipate whether a patient may exhibit additional or more severe side effects from certain cancer treatments.
Oncology Nurses’ Role in Genetics and Genomics
As genetics and genomics become increasingly more commonplace in the treatment of cancer, oncology nurses need to be aware of considerations for patients and their families. For example, patients receiving genetic or genomic testing should always be referred for genetics counseling to help them understand the findings. Genomic testing results can have life-altering implications for both patients and their families if a familial risk factor is found.
Until recently, a few companies offered direct-to-consumer genomic health profiles without a prescription. However, because of concerns about regulation, standardization, and the lack of medical supervision and counseling to interpret the results, the U.S. Food and Drug Administration put a halt on direct-to-consumer genetic testing in November 2013. Oncology nurses need to be aware of the changing regulations and warn patients against these kinds of tests without medical supervision and counseling.
Oncology nurses’ unique role as patient advocates and educators will be critical as genetics and genomics become more widely used in cancer care. Nurses should advocate for their patients as national and institutional policies are developed, then provide education when such testing is used, including helping them interpret and use the results.
For more information on genetics, genomics, personalized medicine, and cancer, refer to the full article by Blix.
Learn more about these important topics when you add Genetics and Genomics in Oncology Nursing Practice to your medical library today.
Five-Minute In-Service is a monthly feature that offers readers a concise recap of full-length articles published in the Clinical Journal of Oncology Nursing (CJON) or Oncology Nursing Forum. This edition summarizes “Personalized Medicine, Genomics, and Pharmacogenomics: A Primer for Nurses,” by Andrew Blix, RN, BSN, BS, which was featured in the August 2014 issue of CJON. Questions regarding the information presented in this Five-Minute In-Service should be directed to the CJON editor at CJONEditor@ons.org. Photocopying of this article for educational purposes and group discussion is permitted.