Cancer Genetics Risk Assessment and Counseling (PDQ®): Genetics - Health Professional Information [NCI] - Components of the Risk Assessment Process
It is also important to consider limited, missing, or questionable information when reviewing a pedigree for cancer risk assessment. It is more difficult to identify features of hereditary disease in families with a truncated family structure due to loss of contact with relatives, small family size, or deaths at an early age from unrelated conditions. When there are few family members of the at-risk gender when considering a particular syndrome with primarily male or female specific disease manifestations, the family history may be difficult to assess (e.g., few female members in a family at risk of hereditary breast and ovarian cancer syndrome). In addition, information collected on risk-reducing surgical procedures, such as oophorectomy, could significantly change prior probability estimation and the constellation of cancers observed in a family. Other factors to clarify and document whenever possible are adoptions, use of donor egg or sperm, consanguinity, and uncertain paternity.
Additionally, family histories are dynamic. The occurrence of additional cancers may alter the likelihood of a hereditary predisposition to cancer, and consideration of differential diagnoses or empiric cancer risk estimates may change if additional cancers arise in the family. Furthermore, changes in the cancer family history over time may alter recommendations for earlier or more intense cancer screening. A descriptive study that examined baseline and follow-up family history data from a U.S. population-based cancer registry reported that family history of breast cancer or colorectal cancer becomes increasingly relevant in early adulthood and changes significantly from age 30 years to age 50 years. Therefore, it is important to advise the consultand to take note of, confirm, and report cancer diagnoses or other pertinent family health history that occurs after completion of the initial risk assessment process. This is especially important if genetic testing was not performed or was uninformative.
Finally, the process of taking the family history has a psychosocial dimension. Discussing and documenting discrete aspects of family relationships and health brings the family into the session symbolically, even when a single person is being counseled. Problems that may be encountered in eliciting a family history and constructing a pedigree include difficulty contacting relatives with whom one has little or no relationship, differing views between family members about the value of genetic information, resistance to discussion of cancer and cancer-related illness, unanticipated discovery of previously unknown medical or family information, and coercion of one relative by another regarding testing decisions. In addition, unexpected emotional distress may be experienced by the consultand in the process of gathering family history information.
Determining Cancer Risk
Analysis of the family history
Because a family history of cancer is one of the important predictors of cancer risk, analysis of the pedigree constitutes an important aspect of risk assessment. This analysis might be thought of as a series of the following questions:
- What is the evidence that a cancer susceptibility syndrome is present in this family?
- If a syndrome is present, what is the most probable diagnosis?
- What could make this family history difficult to interpret?
- What is the most likely mode of inheritance, regardless of whether a specific syndrome diagnosis can be established?
- What is the chance of a member of this family developing cancer, if an inherited susceptibility exists?
- If no recognizable syndrome is present, is there a risk of cancer based on other epidemiological risk factors?