Screenings Key to Identifying Genetic Cancer Risk
Cancer is a common disease, affecting nearly one in two men and one in three women in the United States over the course of a lifetime.
Although cancer is caused by genetic errors, the vast majority of cancers are not inherited. Sporadic cancers occur by chance and account for up to 90 percent of cases. Malignancies develop from mutations acquired after birth and are diagnosed at ages generally consistent within the general population. They are not present in every cell and are not passed down to children.
Less than 10 percent of cancers are hereditary. However, for individuals who inherit cancer-related mutations, the risk of cancer is much higher than for those without the mutation. As a result, it is vital to identify this at-risk population early so we can improve outcomes for these patients.
When an individual inherits a cancer-causing gene, the abnormality is present at birth and contained in every cell. Carriers have a higher risk of developing cancer, and it usually occurs at a younger age. In addition, each of their children has a 50 percent chance of inheriting the mutated gene. Because cancer is complex and multi-factorial, however, not everyone with the inherited mutation will develop cancer.
Among the first genes identified to cause hereditary forms of cancers are the BRCA1 and BRCA2 genes, which belong to a class of genes known as tumor suppressors. The deleterious mutation of these genes has been linked to the development of hereditary breast and ovarian cancer in females. It is important to note that inherited forms of cancer often exhibit peculiar patterns that can be recognized. For breast cancer, these include development at a younger age (below 50), bilaterally, or in conjunction with another form of cancer, such as ovarian. These mutations have also been linked to an increased incidence of breast cancer and prostate cancer in males. So, it is important to remember that these mutations also pass from fathers to their children.
Early identification of those affected by an inherited mutation can be life-saving. For instance, ovarian cancer is difficult to diagnose, and early detection is key to increasing survival rates. When treatment is initiated during stage I, survival rates are 80 to 90 percent. If not detected until stage IV, survival rates drop to 5 percent.
It is therefore imperative for healthcare providers to recognize the importance of screening patients to determine which families may be at increased risk. Screening begins with an assessment of family history to evaluate the potential risk. Patients should be questioned about their personal health history and the history of blood relatives, including parents, grandparents, brothers, sisters, cousins, aunts and uncles on both sides of their families. Questions should include:
- How many individuals developed cancer?
- What types of cancer?
- Are there family members with more than one type of cancer?
- At what age was the onset of cancer experienced?
- Are there bilateral cancers?
- What is the familial connection with the person diagnosed?
- Is there a vertical pattern of inheritance — both parents and children?
The ultimate goal is to identify those at higher risk early, so they and other family members can be tested. If a hereditary risk factor is found, life-saving screenings or prophylactic treatments can be offered. This knowledge allows families to take an active role in screening and prevention options, which can include medication and surgery. Primary care physicians have a responsibility to reduce the burden of this disease for these families. Once identified, options can be recommended to reduce the risk of developing cancer or catch it in its early stages while treatment is most effective.
Dr. Mohamed Khalifa is a board-certified clinical geneticist and director of the Akron Children’s Hospital Genetic Center.
MD News November/December 2011, Cleveland/Akron/Canton
MD News - Screenings Key to Identifying Genetic Cancer Risk
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