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Genetic Testing

05 September 2013 Written by  Chris Scott
Published in July 2013 Articles


Most cancers are caused by genetic changes or mutations in cells. Cancer develops when deoxyribonucleic acid (DNA) is damaged in such a way that it no longer functions correctly.

Most DNA is stored in the chromosomes, where it is compacted and wound up in a coil. All humans have 23 pairs of chromosomes. One of each pair of chromosomes is inherited from each of our parents at the time of conception.

A chromosome can be thought of as a recipe book. When a cell needs to regenerate, the DNA in a chromosome will unwind section by section and an exact copy will be created for the new daughter cell. When the cell needs a specific protein or enzyme, only a section of the DNA will unwind and then code for the desired product. To continue the analogy, the section that unwinds would be a selected recipe. The copy is the product you get from the recipe.

If the recipe is damaged, then the product may not turn out correctly. For example, in the recipe for chocolate chip cookies, if the ingredient "chocolate" in the recipe was mutated or changed to "butterscotch," you would still have a cookie but it just wouldn't taste the same. However, if the ingredient "flour" was mutated or changed to "applesauce," the recipe just would not work, it would be a malignant flaw in the recipe.

The same types of mutations can happen to the copied DNA during replication. Sometimes the mutation is a minor change in a nonfunctioning area and does not signifi­cantly change the protein or new cells, but other times the mutation causes a normal cell to become a cancer cell.

Research has identified some of the environ­mental factors that will cause a normal cell to mutate into a cancer cell. Tobacco exposure, whether first hand or second hand, can cause cancerous mutations in the cells of the mouth, throat, lungs, stomach, colon, pancreas, breast, ovaries, cervix, bladder, kidney, prostate, skin and bone marrow. Consumption of frequent excessive amounts of alcohol (daily consumption equivalent to more than two glasses of wine for men, one glass for women) is associated with cancers of the mouth, throat, esophagus, colon, liver and breast. Sun exposure can cause cancers of the skin. Radiation, pollution, some specific chemicals and viruses are also associated with cancer formation.

Less commonly, the damage to DNA is not from environmental sources, but rather it is inherited from a parent at the time of conception. Research has been able to identify inheritable DNA mutations that put families at increased risk for developing cancer. Inherited cancer syndromes are often associated with clustering of specific cancers within individuals or one side of a family or cancers that occur at younger ages. Genetic counselors or doctors and nurses with specialty training in cancer genetic risk assessment such as those at Contra Costa Oncology, can examine a person's family history to identify persons who should be offered genetic testing. Genetic counseling is an essential part of genetic testing because it helps identify and remedy emotional, financial and health related issues caused by the discovery of a cancer causing, inheritable, genetic mutation.

"New advances in our knowledge of how cancer starts and spreads have allowed us to not only treat malignancies in a more comprehensive and effective way than was possible in the past, but also to identify those individuals at risk of developing cancer before it starts," shares Michael P. Sherman M.D., Ph.D., Medical Director and Founder of Contra Costa Oncology (CCO) in Walnut Creek. The expanding knowledge about the origins of cancer gives health care providers the ability to detect the presence of a malignancy early in its course of development and then to intervene to prevent its spread. Moreover, the advances in cancer screening and prevention, based on genetic testing, have allowed oncologists to give specific recommendations to patients before they have cancer, or find it at a curable stage. New screening strategies for selected individuals at risk include: advanced screening procedures using techniques such as breast MRIs and early colonoscopy, plus life-saving interven­tions such as mastectomy, hysterectomy with oophorectomy, colectomy or prostatectomy. These interventions are changing the oncology landscape and are bringing effective relief and healing to patients.

"Genetic testing is a newer tool for the prevention of cancer," states Kathleen Fitterer, GNP-c, AOCNP, a Nurse Practitioner at CCO who specializes in Oncology care and Cancer Genetic Risk counseling, " but knowing if a person has a genetic mutation that predisposes them to cancer development, allows our team to advise a person regarding advanced screening practices, preventive medicines or cancer preventing surgery." Oncology practices such as CCO are on the forefront of genetic testing and counseling because they continue to encourage both their physicians and nurses to pursue additional studies in Cancer Genetic Risk Assessment through programs like the Oncology Nurses Society and City of Hope's intensive course for Cancer Genetic Risk Assessment.

Though inheritable genetic mutations account for only 5-10% of cancers of the breast, ovarian, colon, uterine, pancreatic, stomach and skin (melanoma), it is vital to know who carries the mutation. Knowing if a person carries a genetic mutation allows healthcare providers to prescribe more intensive screening. "Providing genetic counseling to our patients at Contra Costa Oncology is a unique and exciting part of our practice" says Dr. Vandana Rajagopalan. "I see patients at Contra Costa Oncology who are able to receive genetic counseling in a setting where they feel comfortable and safe, allowing patients to make relevant treatment decisions without delays to care." The goal of intensive screening for these individuals at high risk for cancer development is to detect a cancer in its earliest and most curative stage.

Most recently, Angelina Jolie brought genetic testing to the forefront when she elected to have double mastectomies with reconstructive surgery. Because she had tested positive for the genetic mutation, Jolie had an 85% chance of developing breast cancer by age 70. The average American woman has an 8% chance of getting breast cancer by the age of 70. A woman with no genetic mutation but two close blood relatives with breast cancer has approxi­mately a 15% risk of developing breast cancer by the same age. Jolie's risk reducing mastectomies lowered her chances of getting breast cancer by 89-100% and her overall lifetime risk of developing breast cancer went from 85% down to 8%, the average American woman's risk. Similar risk reducing interventions exist for other inheritable genetic cancer syndromes as well. Families with a strong family history of a cancer should consult their primary care provider to learn if they are eligible for genetic testing.

For these high-risk individuals, medications, surgery, and life style changes can be prescribed to minimize the risk of cancer formation. According to Dr. Diana Superfin of Contra Costa Oncology, "there are lifestyle choices that can help fortify our bodies against cancer formation." A diet rich in vegetables and fruit (10 servings per day), whole grains, low or nonfat dairy and supplemented with lean meats provides the nutrients our bodies need to recover from exposure to toxins. Exercise (35 minutes five or six days per week) is associated with less risk of getting cancer. Maintaining a healthy body weight also reduces the risk of cancer formation. Quitting tobacco usage starts a recovery process that, with time, reduces that person's risk of developing cancer.

If you are interested in exploring your cancer risk, please visit the genetics tab on the Contra Costa Oncology website (www. contracostaoncology.com). There, you can take a confidential quiz to assess your personal risk. Links to reputable websites are also available to learn more about cancer, cancer treatment, and cancer genetics.

Read 3146 times Last modified on Thursday, 05 September 2013 05:35
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