|Up to 15% of all
cancers have a familial basis. That means that the cancer tends to occur
among members of a family. Much of the time, different types of cancer occur
apparently by chance, or in association with common family habits such as
cigarette smoking. However, studies have suggested that certain cancers can
occur to excess in some families. For example, a woman whose mother and/or
sisters (first-degree relatives) had breast cancer is 2-3 times more likely
to develop breast cancer than a woman whose close female relatives have not
had breast cancer. Many other cancers are associated with having a family
history of that cancer. Breast, ovarian, prostate and colon are some of
these cancers. There are genetic tests for breast, colon and melanoma
available ( genetics counselors
here.) Myriad now has a panel
that will test for 25 genes associated with cancer
here and here)
Genetic mutations that can be passed along to new generations (germ line mutations) would cause familial cancers where family history is important. Most cancers are caused by genetic mutations that occur after birth (somatic cell mutations) and not inheritable (see cancer genomics below) and read the NCI section on cancer genetics here.
Cancer Genomics. The management of cancer is shifting to targeted therapy based on the specific gene mutations that have occurred in the cancer, For instance with adenocarcinoma of the lung if there is an EGFR (epidermal growth factor) mutation then the targeted drug erlotinib (Tarceeva) would be used and for individuals with fusion of the ALK Gene (Anaplastic Lymphoma Kinase) would be treated with crizotinib (Xalkori). The NIH has a site (The Cancer Genome Atlas) to keep researchers up to date on the rapid changes in this field. To understand the genetic basis of cancer go here.
Several tumor suppressor genes have been identified, predominantly
through studies of cancer-prone families with hereditary cancers. Major recent genetic
discoveries include the identification of BRCA1, a gene for hereditary breast and ovarian
cancer, the localization of BRCA2 and another breast cancer gene. Approximately 5 percent
of breast or colon cancer patients might carry one or more inherited susceptibility genes.
The discovery of these genes has increased greatly the numbers of cancer susceptibility
gene carriers who can possibly be identified. For detailed information about genetics, and
genetic testing go to the NCI site here and
for more on breast cancer go here.
|The general clinical features
that raise the suspicion of a familial form of cancer susceptibility in a
patient diagnosed with any type of malignancy include:
How genes cause