Epidemiology of Cancer

Epidemiology of Cancer:

• Over last 50 yrs, the overall cancer death rate has significantly incr for men; for women, it has fallen slightly
• Increase in men is due to lung cancer
• Improvement for women is due to decline in death rates from cancers of uterus, stomach, liver, and carcinoma of the cervix
• Carcinoma of the lung has incr in both sexes; beginning to decline in men, but still incr in women
• Carcinomas of breast are 2.5X more frequent than carcinomas of lung, but lung cancer is leading cause of cancer deaths in women
• Decrease in death from stomach and liver carcinomas – perhaps due to decr in dietary carcinogens

Cancer incidence and cancer death for men:

Cancer incidence and cancer deaths for women:

Geographic and Environmental Factors:

• Much of geographic differences are consequences of environmental influences
• Rates of cancer for immigrants comes closer to US rates of cancer with each succeeding generation

Environmental Factors:

1. UV rays
2. Asbestos, vinyl chloride, 2-naphthylamine 

• Persons more than 25% overweight have a higher death rate from cancer
• Alcohol – incr risk for carcinomas of oropharynx, larynx, esophagus, and liver
• Smoking – incr risk for cancer of mouth, pharynx, larynx, esophagus, pancreas, bladder, and lung dz
• Smoking is single most important environmental factor contributing to premature death in the US
• Alcohol and tobacco together – incr risk of cancers in upper aerodigestive tract
• Risk of cervical cancer is linked to age at first intercourse and the number of sex partners

Age:

• Each age group has its own predilection to certain forms of cancer
• Striking incr in mortality from cancer in 55-74 y/o
• Under 15 y/o:
• Cancer accounts for about 10% of deaths in this group
• Most common is acute leukemia and neoplasms of the CNS

Heredity:

• For a large number of cancers, there are environmental influences and hereditary predisposition’s

Inherited Cancer Syndromes – inheritance of a single mutant gene greatly incr risk of developing a tumor

• Tumors involve specific sites and tissues
• Tumors w/in this group are often associated w/ a specific marker phenotype
• Both incomplete penetrance and variable expressitivity are noted

Familial Cancers

• Almost all sporadic cancers have been reported to occur in familial forms
• Early age at onset, tumors arising in two or more close relative of index case, and sometimes multiple or bilateral tumors
• Not associated w/ specific marker phenotypes

Autosomal Recessive Syndromes of Defective DNA Repair:

• Example is xeroderma pigmentosa

Autosomal Dominant Neoplasia Syndromes

RB, retinoblastoma; FAP, familial adenomatous polyposis; APC, adenomatous polyposis coli; MEN, multiple endocrine neoplasia; RET, rearranged during  transfection; VHL, von Hippel-Lindau.

Defective DNA Repair Syndromes

• ATM, ataxia-telangiectasia mutated.
• *Ataxia-telangiectasia is also associated with cerebellar ataxia.

Acquired Preneoplastic Disorders:

• A premalignant lesion is an identifiable local abnormality associated with an increased risk of a malignant tumour developing at that site. 
• In the great majority of cases, no malignant neoplasms emerge
• Certain forms of benign neoplasia also constitute precancerous conditions
• Example – villous adenoma of the colon
• Most benign neoplasms do not become cancerous

Precancerous (Premalignant) Lesions.