Description

Some people in British Columbia have more relatives with cancer than provincial rates predict. In other families, there are fewer cases than expected. Familiar clustering is the tendency for disease to occur in people who have affected relatives. It can happen because relatives share genetic material and/or environmental exposures, or it can happen by chance. The identification of new familial cancer syndromes will be hastened by observations of familial clustering in the population. Cancer family history depends on a person's age and the size/structure of his or her family. The distribution of family size and structure in BC is not known. A recent Statistics Canada report described the tendency for men and women to have children with more than one partner, thereby increasing the number of half-siblings in the population. Whether this will affect our ability to identify familial clustering is not known. The proposed research will answer this question.

Genetic testing for cancer susceptibility has most often concerned BRCA1 and BRCA2, and the association with breast and ovarian cancer risk. Recently, genetic tests have been described for susceptibility to colorectal cancer, skin cancer and prostate cancer. Despite the availability, many people are expected to decline testing because of concerns about privacy and other factors. People's desire for genetic testing and counseling services is important for health care services planning.

A pilot mail survey found that women were more likely to participate than men, but willingness to respond did not depend on age or place of residence. (Surveys were mailed to a random sample of people living in the Greater Vancouver Regional District.) Details of family history were generally complete, but details were often unknown for unknown for distant relatives. The main factors influencing interest in genetic testing and counselling were the possibility of preventing cancer, and concerns about the health of family members. A larger study is recommended to confirm these results.