Epidemiology of cancer

Epidemiological studies provide major insights into origin of cancer occurrence magnitude of cancer problems and factors relating to patients and environment that influence predisposition to cancer

Environmental factors:

Dominant risk factors hence preventable

an evidence is there high breast cancer deaths in the US and Europe than Japan

They include:

- Diet - smoked fish is related to cancer

Obesity and food additives and contaminates is associated with increased risk of developing cancer

- Smoking - cigarettes increase risk of lung cancer

- alcohol consumption - liver cirrhosis leading to liver cancer

- Infectious agents - radiations cause skin cancer

Viruses -hepatitis B and C cause hepato-carcinoma and HIV causes Kaposi’s sarcoma. Papilloma virus causes cervical cancer

Parasites cause schistosomiasis

- Reproductive history for example human papilloma virus transmitted through sex causes cervical cancer

- Age and cancer – Frequency of cancer increases with age mostly 55 to 75 years Due to accumulation of somatic mutations that drives emergence of malignant neoplasms and decline in immune competence

Cancer is also responsible for more than 10% of deaths among children less than 15 years. The major cancers t are leukemia’s, tumors of central nervous system , lymphomas and bone sarcomas.

Genetic factors:

Refers to family history of mutations affecting the function of tumor suppressor genes

There is a strong relationship between hereditary susceptibility and environmental carcinogenic stimuli e.g.

Inheritance of mutated copies of BRCA1 or BRCA2 causes breast cancer

Retinoblastoma in children

Mongols are at a high risk of getting leukemia

Acquired predisposing factors:

- Chronic inflammation creates a fertile “soil” for development of malignant tumors

- Immunodeficiency state promotes virus induced cancers

- Precursor lesions promotes squamous metaplasia and dysplasia of bronchial mucosa

- Endometrial hyperplasia and dysplasia in women with unopposed estrogenic stimulation leads to endometrial carcinoma