Among the genetic and personal factors age, sex, race, marital status, etc. have much to do about the prevalence of cancer.
Age
The prevalence of cancer increases with age. Man is particularly vulnerable after the age of 50. It is not certain whether this is due to a) the changes in the body due to the ageing process, b) a long incubation period of cancer or c) long exposure to a carcinogen or cancer causing substance.
Sex
There are sex differences in the frequency of cancer, e.g. lung cancer and cancer of the oesophagus are more common in men than in women.
Race
The influence of race is difficult to disentangle from that of environment. Fair-complexioned individuals have an excessive frequency of cancer of the skin especially of the face and neck than coloured races.
Marital Status
Cancer cervix is more common among the married and among those who marry at an early age.
Heredity
Genetic influences have long been suspected. Napolean is said to have died of cancer of stomach; his grandfather, father, brothers and sisters, all died of cancer of stomach. Retinoblastoma, i.e. cancer of the eye occurs in the children of the same parents. Osteosarcoma or malignant cancer of the bone, polyposis colon or cancer of colon and thyroid cancers in twins, are other examples. It is recognised that mongols are more likely to develop cancer or “blood cancer” (leukaemia) than normal children. There are strong indications that chromosomal damage and deformity is characteristic of some forms of cancers, but a definite cause-effect relationship has not been established.
Socio-economic Status
There is a definite relationship between socio-economic status and cancer frequency. For example, cancer of stomach, skin and cervix are more common in low income than in high income groups. Breast cancer is commoner among women of higher socio-economic group, probably because of late child-bearing.