Definition of Cancer :

Cancer : Cancer may be regarded as a group of diseases characterized by –

• An abnormal growth of cells.
• Ability to invade adjacent tissues and even distant organs, and
• The eventual death of the affected patient if the tumor has progressed beyond that stage when it ca be successfully removed.
• Cancer can occur at any site or tissue of the body and may involve any type of cells.

Major categories of cancer :

1. Carcinomas : Arising from epithelial cells lining the internal surfaces of the various organs (e.g mouth, esophagus, intestines, uterus) and from the skin epithelium.
2. Sarcomas :  Arising from mesodermal cells constituting the various connective tissues (e,g. fibrous tissue, fat, and bone).
3. Lymphomas, myeloma and leukaemias :  Arising from the cells of bone marrow and immune systems.

Warning signs/danger signs of cancer :

1. Unusual bleeding or discharge from any natural orifices.
2. A lump or thickening of the breast or elsewhere.
3. A sore that does not heal.
4. Change in bowel or bladder habit.
5. Hoarseness or persistent cough.
6. Constant indigestion or difficulty in swallowing.
7. A change in want or mole.

Causes of cancer :

A) Environmental factors :

 1) Tobacco : Cancer of the lung, larynx, mouth, pharynx, esophagus, bladder, pancreas, and probably kidney.

 2) Alcohol : Esophageal, liver and rectal cancers.

 3) Dietary factors : Smoked fish is related to stomach cancer, dietary fiber to intestinal cancer, beef consumption to bowel cancer and a high fat diet to breast cancer.

 4) Occupational exposures : Exposure to benzene, arsenic, cadmium, chromium, vinyl chloride, asbestos, polycyclic hydrocarbons, etc.

 5) Viruses :

• Hepatitis B & C: Hepatocellular carcinoma. 
• HIV infection : Kaposi’s sarcoma, non-Hodgkin’s lymphoma.
• Epstein – Barr virus (EBV) : Burkin’s lymphoma and nasopharyngeal carcinoma.
• Cytomegalovirus (CMV) : Kaposi’s sarcoma.
• Human papilloma virus (HPV) : Cancer of cervix.
• Human-T cell leukaemia virus : T-cell leukaemia/lymphoma.

 6) Parasites : Schistosomiasis: Carcinoma of the bladder.

 7) Customs, habits and life-styles :

• Smoking : Lung cancer.
• Tobacco & betel chewing : Oral cancer.

 8) Others : Sunlight, radiation, air and water pollution, medications (eg estrogen) and pesticides.

B) Genetic factors :  For example, retinoblastoma occurs in children of the same parent.

Cancer emergencies :

1. Superior vena cava syndrome (features of superior venacaval obstruction).
2. Pericardial effusion.
3. Intestinal obstruction.
4. Urinary retention.
5. Biliary obstruction.
6. Airway obstruction.
7. Raised intracranial pressure.

Most Common cancers in male :

1. Bronchogenic carcinoma
2. Laryngeal carcinoma
3. Cancer of oral cavity
4. Lymphoma
5. Pharyngeal cancer
6. Carcinoma of unknown primary site (CUP)
7. Bone cancer
8. Cancer of eyes and Lacrimal gland
9. Brain cancer
10. Skin cancer (including melanoma).

Most Common cancers in female :

1. Cervical cancer.
2. Breast cancer.
3. Cancer of oral cavity
4. Lymphoma
5. Carcinoma of oesophagus.
6. Carcinoma of body of uterus.
7. Carcinoma of lungs.
8. Ovarian cancer.
9. Carcinoma larynx.
10. Carcinoma of unknown primary site (CUP).

About cancer screening :

Cancer screening :

Individuals above age 35 years, who can afford it, may undergo a thorough annual medical check-up by a competent physician, with a view to detect early cancers. Laboratory tests may also be carried out as indicated.

While a complete medical history may provide symptoms of a localized or generalized cancer,a thorough physical examination is likely to reveal cancers of the skin, mouth, thyroid, breast, Uterus, vagina, rectum, penis and testicle

Investigations for cancer screening :

1. A chest or other X-ray, as indicated, could provide evidence of lesions in the chest, pleura, lungs and bone.
2. A blood count (CBC) not infrequently provides the initial findings of leukaemias, multiple myelomas, or other blood dyscrasias. Blood biochemistry provides proof of liver and kidney damage.
3. A positive stool examination for blood may point to a GI tract cancer.
4. Pap smear screening may reveal a lesion of the cancer cervix.
5. Mammography helps in the early diagnosis of breast cancer.
6. Sigmoidoscopy may reveal colorectal cancers.

Cancer prevention :

Primary prevention : 

1. Lifestyle modification : Tobacco, alcohol, diet, occupation, personal hygine.
2. Chemo-prevention : Antioxidant vitamins, NSAID), retinoids.
3. Screening tests : Such as pap smear, mammography etc.

Secondary prevention :

1. Cancer registration
2. Early diagnosis:

   .By observation (skin, mouth external genitalia, cervix).

   .By palpation breast, thyroid, rectum, anus, prostate, testes, ovaries, uterus).

   .By investigation (chest X-ray, mammography, sygmoidoscopy).

3. Treatment : Treatment options are

• Surgery
• Radiotherapy
• Chemotherapy

Role of primary prevention in controlling cancer :

Role of primary prevention in controlling cancer : Advancing knowledge has increased our understanding of causative factors of some cancers and it is now possible to control these factors in the general population as well as in particular occupational groups.

Example :

1. Control of tobacco: Reduces incidence of lung cancers and other cancers related to tobacco consumption.
2. Personal hygiene : Improved personal hygiene reduces certain type of cancers e.g. Ca cervix.
3. Occupational exposure : If proper measures are taken to protect the persons from exposure to carcinogens related to occupation, the incidence of cancers will be reduced.
4. Immunization : e.g. against hepatitis B & human papilloma virus etc.
5. Foods, drugs and cosmetics : To be tested for carcinogens before use.
6. Air pollution : If air pollution is controlled properly, incidence of lung cancer will be reduced.
7. Legislation.
8. Cancer education.

Life style as a determinant of cancer :

• Tobacco : Cancer of the lung, larynx, mouth, pharynx, esophagus, bladder, pancreas, and probably kidney.
• Alcohol : Esophageal, liver and rectal cancers.
• Dietary factors : Smoked fish is related to stomach cancer, dietary fiber to intestinal cancer, beef consumption to bowel cancer and a high fat diet to breast cancer.

The role of different agent factors in developing cancer :

Agent factors in developing cancer :

1. Physical agents : e.g. UV radiation – development of skin cancer.
2. Mechanical irritation : e.g. chronic irritation and trauma to the cervix-uteri from multiple child birth and chronic cervicitis may lead to cancer of the cervix.
3. Chemical agents : e.g, dye workers – bladder cancer, asbestos workers- lung cancer.
4. Nutrition : Smoked fish is related to stomach cancer, dietary fiber to intestinal cancer, beef consumption to bowel cancer and a high fat diet to breast cancer.
5. Viral and parasitic agents:

Viruses :

• Hepatitis B & C: Hepatocellular carcinoma.
• HIV infection : Kaposi’s sarcoma, non-Hodgkin’s lymphoma.
• Epstein Barr virus (EBV) : Burkitt’s lymphoma and nasopharyngeal carcinoma
• Cytomegalovirus (CMV) : Kaposi’s sarcoma.
• Human papilloma virus (HPV) : Cancer of cervix
• Human – T cell leukaemia virus : T-cell leukaemia / lymphoma.

Parasites :

• Schistosomiasis : Carcinoma of the bladder