Are You And Your Family At Risk Of Cancer?

By: Dr Peter Ang, Consultant, Dept of Medical Oncology, NCC

Cancer is a common disease, and majority of the cases are sporadic. Purely by chance, many cases of “common” cancers, e.g. breast, colon and lung cancers can appear to run in a family. Other risk factors which are not genetic such as diet, smoking and environmental exposures can also lead to clustering of cancer cases within a family.

However, in some families, multiple cases of cancer can occur in several generations or at younger ages. In these circumstances, genes carrying harmful alterations may be involved. Since there is no simple genetic screening test available presently that can determine this, a detailed 3-generation family history is the starting point to assess an inherited risk of cancer.

If history makes one suspect an inherited cancer, then one can consider genetic tests starting with an affected family member. Currently, these tests are labour-intensive and costly, and are positive in only about 50% of the affected families. So even if the test is negative in an affected family with strong suspicion for inherited predisposition to develop cancers, it does not mean that one can do away with the need for close follow-up.

Testing positive for an alteration in the DNA may raise the probability of developing a certain type of cancer. However, it is not a prediction that an individual will develop cancer. The potential benefit of a positive genetic screen depends on the availability, acceptability and efficacy of increased surveillance techniques and preventive options such as prophylactic surgery or chemoprevention (using medication to prevent or reduce the risk of cancer). Such benefits may be magnified when there are several at-risk family members willing to be screened for a specific cancer causing mutation. Given the complexity and uncertainty on genetic screening, referral to a health care professional with interest in familial cancers should be considered. Appropriate referral enables an individual to discuss the risks and benefits of testing that would lead to making an informed decision on genetic testing.

When these individuals seek counseling and management at NCC’s Risk Evaluation and Prevention (REAP) Clinic, a detailed family history is taken first to assess the risk of a hereditary cancer affecting the family. If a suspicion is raised, then risks and benefits of DNA based testing are discussed at length. Decision to undergo such testing is complex and has to be made by a family after careful consideration of all the pros and cons. For more information about the REAP Clinic, please call the Cancer Helpline on tel: 6225 5655 or email cancerhelpline@nccs.com.sg>.