Worldwide biostatistical studies indicate that approximately 15% to 16% of the population will succumb to cancer. However, these statistics include the total population at risk and do not reflect the many families which may show increased frequencies of cancer ("cancer-susceptible" genotypes), nor those showing a paucity of neoplasms ("cancer-resistant" genotypes).
Simple mendelian factors have been shown to cause cancer resistance as well as cancer susceptibility in inbred strains of mice. However, with respect to carcinoma in man, other than a few clinical syndromes such as neurofibromatosis, familial polyposis coli, basal cell nevus syndrome, Gardner's syndrome and xeroderma pigmentosum, simple genetic factors have not been the rule. This has led those who are unsophisticated in medical genetics to discredit genetics as a factor in cancer development because they cannot readily identify a definite genetic pattern in human family histories.1 However, many cancers, ie, carcinoma of the prostate, breast, stomach, and malignant
"CANCER FAMILIES". JAMA. 1966;195(13):1145-1146. doi:10.1001/jama.1966.03100130119036