Cancer and Genetic Causes Term Paper

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Family history of cancer and pre-Disposition of a person to cancer

Family Cancer Syndromes

DNA, genes, and chromosomes

Family cancer syndromes - when should I worry?

Family History and Prevalence of Certain Types of Cancer

Risk Assessment in Identifying a Family History of Cancer

Family Cancer Syndromes

Cancer has become a common disease in the world today and the prevalence of the disease is such that in many families one would find at least one person who has been affected by the disease. There have been instances where it has been noted that some forms of cancer tend to run in some families.

Often researchers point to certain common risk factors like smoking among the family that can lead to many types of cancer. Other factors like obesity that tend to run in families also have an influence in the prevalence of cancer in the family (www.cancer.org).

However in some cases it has been found that a set of abnormal gene that is passed along from generation to generation in a family is the cause of cancer. Even as this phenomenon is often termed as inherited cancer, it is the defective or abnormal gene that is inherited and which leads to the development of cancer in individuals of a particular family that has carries the abnormal gene. Research has shown that cancers that results directly from gene defects -- called mutations, accounts for about 5% to 10% of all cancers (www.cancer.org).

DNA, genes, and chromosomes

Abnormal gene -- pieces of DNA, are the cause of cancer. The genes carry information for cells to make the proteins that the body needs, to destroy damaged cells and maintain balance of cells in the body. All aspects of human body such as hair color, eye color, and height are controlled by gene. The chance of development of cancer is also partly controlled and affected by gene.

Mutation is the term given to the abnormal change in a gene. The 2 types of mutations of change in gene character are inherited and acquired.

There are 2 copies of most genes -- one from each parent and cells start out with one mutation when there is a genetic abnormality. Cancer susceptibility gene is created when the other copy of the gene stops working due to an acquired mutation which can lead to development of cancerous cells and foster development of tumors.

Family cancer syndromes - when should I worry?

While certain causes of cancer running in the family could be due to bad habits like smoking, there are some are caused by inherited gene mutation that results in a family cancer syndrome.

There are certain things that result from family cancer syndrome like in cases of an uncommon or rare type of cancer such as kidney cancer, cancers that develop at a young age, when there is multiple cancer types in a single individual such as breast and ovarian cancer in a woman, when both pair of organs develops cancer as in both kidneys or breasts, when more than one childhood cancer is found in siblings and in cases of cancer developing in the sex not usually affected such a breast cancer developing in a man.

Family History and Prevalence of Certain Types of Cancer

Breast Cancer

After non-melanoma skin cancer, breast cancer is the most common and frequently detected cancer in women and causes more deaths than all other forms of cancer other than lung cancer. Studies have found that among adult populations, 5% to 10% of women belong to a family where either mother or sister have or had breast cancer. The prevalence is doubled for either a first-degree relative (FDR) or a second-degree relative with breast cancer (3). In case-control and cohort studies (Dungan).

By the use of volunteer and population-based samples, several studies have assessed the risk of development of breast cancer. Several studies pooled together found out that the relative risk of breast cancer is 2.1 with a 95% confidence interval. The number of relatives affected by breast cancer, the age of an individual at diagnosis, the prevalence of bilateral or multiple ipsilateral breast cancers in a family member and occurrence of breast cancer in male relatives are the factors that increase the risks of developing the disease (Colditz).

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Women whose mother or sister has breast cancer runs a significantly greater risk of developing the disease was found out after a study based on the Swedish Family Cancer Database. The study found out that the hazard ratio for women who have just one instance of the disease in the cancer was 1.8 compared to a value of 2.7 for women belonging to a family with a history of multiple breast cancers (Kerber and O'Brien).

Ovarian Cancer

While reproductive complications, demography and lifestyle are factor that can lead to the development of ovarian cancer, a family history of the disease is one of the single most common reasons for the disease. Risk of ovarian cancer was found to have a ratio of 3.1 in families with a history of the disease in a large meta-analysis of 15 published studies.

Prostate cancer

There have been frequent reports of familial clustering of prostate cancer in a way similar to breast and colon cancer (12-16]. High-risk inherited genetic factors of family history of prostate cancer susceptibility genes are believed to be the reason behind 5% to 10% of prostate cancer cases. Family history has been found out to be a major risk factor in prostate cancer in research results and studies involving large case-control studies and cohort studies that are representative of various populations (Friebel, Domchek and Rebbeck). While the risk is increased by prevalence of the disease in the family, it is inversely proportional to age -- i.e. families with prostate cancer history have the chance of developing the disease at a young age than the normal population. Several studies related to prostate cancer described population-based series even as many of the studies examined risks associated with family history (Chlebowski et al.). The data collected from the latter is generalizable.

A meta-analysis that comprised of 33 epidemiologic case-control and cohort-based studies found out that men were a greater risk when their family had brothers with the disease than those where the father is affected by it. X-linked or recessive inheritance is believed to be the possible reason even though the actual reason in the difference in the risk is yet not ascertained. The number of close relatives affected by the disease has been found to directly proportional. The incident of first degree relatives being affected by prostate cancer before age 65 years also increases the risk directly.

Endometrial Cancer

The risk of a woman developing endometrial cancer is significant due to family history even though the hyperestrogenic state is considered to be the most common predisposing factor the disease. Hereditary reasons are believed to be the case of this disease in approximately 3% to 5% of uterine cancer cases in women (Weissman, Weiss and Newlin). Lynch syndrome is the primary hereditary endometrial cancer syndrome. Lynch syndrome is believed to have a population prevalence of 1 in 300 to 1 in 1,000 individuals (Elfayomy and Soliman)

Risk Assessment in Identifying a Family History of Cancer

While assessing the risk factor of cancer related to family history, it is important that the information collected is accurate and complete. In case an individual is unaware of relatives affected with cancer the assessment of family history would be erroneous. Information obtained from a family history of cancer can be limited due to small family size, non-contact with family members and premature deaths in the family.

There are also variants in the risk factors with respect to sex. For example, breast or ovarian cancer risks in a family involves distant relatives on the paternal side than on the maternal side and this can lead to inaccurate assessment of family heritage risk of such cancers as information may be more difficult to obtain.

Conclusion

Form the discussions above it can be concluded that the prevalence of certain types of cancer have been found to be linked to family history of the disease. The risk factor for breast, ovarian, prostate and endometrial cancer is directly linked to a family history of the disease. However the prevalence is dependent on a number of factors within the family history including age, sex and close or distant relations with an individual......

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