Biology of Disease

(backadmin) #1

clearly, some cancers occur only in men or women. Obvious examples of
the latter are cancer of the cervix uteri or ‘cervical cancer’ in women and
testicular and prostate cancer in men. Contrary to common belief, men
can develop breast cancer, although the incidence is much lower than in
women. Moreover, the incidence of breast cancer in both sexes appears to be
increasing. A study in the USA showed increases in male and female breast
cancer of 26% and 52% respectively between two separate studies in 1973–
1978 and 1994–1998. The commonest forms of cancer in men, women and
children in the USA are shown in Table 17.1.


Men Women Children

Prostate cancer breast cancer leukemias

Lung cancer lung cancer brain tumors

Colorectal cancer colorectal cancer lymphomas

Table 17.1Commonest forms of cancer in the US population


The annual incidence of different forms of cancer is shown in Figure 17.2. With
the exception of the childhood cancers, the incidence of cancer increases with
age, as shown in Figure 17.3. This increasing incidence is due to a number
of factors including increased length of exposure to environmental agents
associated with cancer, and an accumulation within cells of mutations in
the DNA (Chapter 18), coupled with decreased efficiency of the cellular DNA
repair mechanisms. In addition the immune system, which may play a role
in eliminating early cancerous cells, also decreases in efficiency with age and
this may lead to a failure to eliminate malignant cells as they arise.


Figure 17.2Annual incidence of different forms of cancer in the UK. Statistics obtained from
the Office for National Statistics, UK (2005).


EPIDEMIOLOGY OF CANCER

CZhhVg6]bZY!BVjgZZc9Vlhdc!8]g^hHb^i]:YLddY ),,


Number of registrations

40000

35000

30000

25000

20000

15000

10000

5000

0

Female
Male

Mouth and pharynx

EsophagusStomach

Rectosigmoid junction

Colon RectumProstateOvariesKidneyPancreas

Bronchus and lung

Malignant melanoma of skin

Breast
Free download pdf