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Cancer Genetics

Cancer in the Family



We are a family of thirteen children, there are only nine of us still alive I am the youngest at 47. We had a brother die at the age of seven with cancer, my father was diagnosed in 1966 with stomach cancer & later died at the age of 83 from prostate cancer, in 1991 my oldest sister died from cancer that was first found in her lungs in September of that year and died two months later,never smoked or drank, now we have a sister of just 60 years old who has been diagnosed with cancer and is not expected to live can you tell me if genetics has anything to do with this and what the likelihood is of this happening to me or one of my eight siblings?


It is important to know exactly what kind of cancer occurred in each family member and the age of onset. I have included an answer from a previous question to help you understand the issues in familial cancer.

Cancer is a group of more than 100 different diseases. It is the end result of mistakes that occur in the DNA, the code responsible for the structure, growth, and function of the cell. These mistakes can change the normal growth control of the cell. It is the accumulation of multiple DNA mistakes or changes over many years that allows a normal cell to become abnormal, grow without control, and eventually become a cancer. The majority of cancer occurs in the absence of a significant family history and is caused by these acquired DNA changes. These changes are often a result of environmental and hormonal exposures. Acquired DNA changes cannot be passed from one generation to the next so this type of cancer is considered sporadic (a chance event) and not hereditary.

A single inherited factor is felt to be responsible for about 5-10% of all cancers. Inherited DNA changes are passed down to us from our mothers or fathers through the egg or sperm. Individuals born with a single change in a particular section of the DNA involved with cancer susceptibility will have a much greater chance for developing certain cancers in their lifetime. However, not everyone with a cancer susceptibility gene will develop cancer. Since 5-10% of ALL cancers may be inherited,it is more important to look at the pattern of cancer occurrence in the family than to look at a specific kind of cancer; for instance, if you have two first degree relatives with the same kind of cancer. A first degree relative is a parent, sibling, or child. Other red flags include:

1) Cancer that occurs at an unusually young age. [Prostate cancer at age 38, when it usually occurs at age 60 or older.]

2) Cancer that occurs in multiple primary sites within the same organ. [Different tumors in the colon in different sections of the colon.]

3) Associated cancers in several close relatives. [Breast cancer and ovarian cancer; colon cancer and uterine cancer; melanoma and pancreatic cancer.]

4) Cancer in an unusual sex. [Male breast cancer.]

5) A primary cancer occurring in paired organs. [Breast cancer occurring in both breasts; eye tumors in both eyes.]

6) An individual who has had two or more primary cancers. [Ovarian cancer diagnosed after breast cancer.]

7) An individual who has been diagnosed with a known hereditary cancer. [Familial adenomatous polyposis or multiple endocrine neoplasia.]

8) A rare or unusual tumor type. [Cancer of the small bowel.]

You may wish to check out the web sites included with this response to check your own family history and to locate a certified genetic counselor in your area.

Related Resources:

Cancer Genetics: Building and Understanding Your Medical Family History
PDQ -- NCI's Comprehensive Cancer Database

For more information:

Go to the Cancer Genetics health topic, where you can:

Response by:

Judith A Westman, MD Judith A Westman, MD
Associate Professor, Clinical Internal Medicine, Pediatrics and Medical Biochemistry
College of Medicine
The Ohio State University