This is the commonest
cancer in males and second commonest cancer in females after breast cancer.
It is also the most preventable cancer
as over 90% is directly related to cigarette smoking. For practical purposes lung
cancer can be divided into small cell lung cancer, comprising about 20 percent
and non-small cell lung cancer, comprising 80 percent.
In non small
cell lung cancer surgery should be considered in all cases although only one quarter
of patients will be operable and only one quarter of them will be cured. Radiotherapy
may provide useful palliation in inoperable patients and very good symptom relief
in metastatic disease.
Chemotherapy is still experimental in non small
cell lung cancer and its role is not yet established. In small cell lung cancer
the disease has almost always disseminated by the time of diagnosis and surgery
is thus inappropriate.
As opposed to non small cell lung cancer, this
tumour is very chemo sensitive and radiosensitive and the majority of patients
will respond to combination chemotherapy (eg, mitomycin, ifosfamide and cisplatin)
with good relief of symptoms and modest prolongation of life.
A small
proportion of limited small cell lung cancer patients will be cured. In patients
with extensive disease, who are incurable, single agent etoposide orally or intravenously
is a possible alternative to combination chemotherapy.
As in non small
cell lung cancer, radiotherapy can provide very useful palliative relief.This
is the most common malignant tumour in the western world and now the third most
common cause of death in the UK after heart disease and pneumonia.
Mortality
rates worldwide are highest in Scotland, closely followed by England and Wales.
In the UK, 35000 people die each year from bronchial carcinoma, with a male to
female ration 3.5 : 1.
Although the rising mortality from this disease
has leveled off in men, it continues to rise in women, accounting for 1 in 8 of
all deaths from malignant disease in women, second only to carcinoma of the breast.
The strength of the association between cigarette smoking and bronchial
carcinoma overshadows any other aetiological factors but there is a higher incidence
of bronchial carcinoma in urban compared with rural areas, even when allowance
is made for cigarette smoking.
Passive smoking (the inhalation of other
people’s smoke by non smokers) increases the risk of bronchial carcinoma
by a factor of 1.5. Occupational factors include exposure to asbestos, and an
association is also claimed for workers in contact with arsenic, chromium, iron
oxide, petroleum products and oils, coal tar, products of coal combustion and
radiation.
Tumours associated with occupational factors are mostly adenocarcinomas
and appear to be less related to cigarette smoking. Bronchial carcinoma accounts
for more than 50 percent of all male deaths from malignant disease.
It is more common in men than women although the gap between the sexes is now
narrowing and occurs most frequently between the ages of 50 and 75 years.
Cigarette smoking is responsible for most cases of bronchial carcinoma and
the increased risk is directly proportional to the amount smoked and to the tar
content of the cigarettes.
For example the death rate from the disease
in heavy cigarette smokers ins 40 times that in non smokers. The incidence is
slightly higher in urban than in rural dwellers presumably because of atmospheric
pollution.
There is a higher incidence of bronchial carcinoma in pulmonary
fibrosis induced by the inhalation of asbestos.This is an uncommon tumour occurring
in a younger age group than carcinoma and affecting equally females and males.
Although classified as a benign tumour it possesses some of the properties
of a malignant growth and may eventually metastasise. There are two histological
types of bronchial adenoma, the relatively more common bronchial carcinoid and
the rare cylindroma (adenoid cystic carcinoma) which often arises at the tracheal
bifurcation.
This rare tumour resembles intestinal carcinoid tumour and
is locally invasive, eventually spreading to mediastinal lymph nodes and finally
to distant organs. It is a highly vascular tumour that projects into the lumen
of a major bronchus causing recurrent haemoptysis.
It grows slowly and
eventually blocks the bronchus, leading to lobar collapse. Rarely, it gives rise
to the carcinoid syndrome. These are extremely rare tumours that may grow in the
bronchus or trachea, causing obstruction.
