Epidemiology of cancer:

Cancer incidence:  In males: Cancers of the lung, prostate, and colon are the leading causes of cancer deaths.  In females : breast, lung, and colon cancers are the most common types.

Geographic and environmental factors:  Environmental factors influence the occurrence of specific types of cancer in different parts of the world.  In Japan the death rate from cancer of the stomach is about seven times that in USA

Environmental carcinogens can be found in:  Food  In personal practices (e.g. cigarette smoking and chronic alcoholic consumption),  Can be universal as sunlight,  limited to certain occupation (e.g. asbestos).

The age: The frequency of cancer increases with age Why?  1-Accumulation of somatic mutations associated with the emergence of malignant neoplasms.  2- Also, the immunologic defenses of the elderly may be less effective than those of the young people.  NB certain cancers are common in children under 15 years old e.g. neuroblastoma, retinoblastoma, leukemias, lymphomas, and Wilms' tumour of the kidney.

NB certain cancers are common in children under 15 years old e.g.  neuroblastoma,  retinoblastoma,  leukemias,  lymphomas,  Wilms' tumour of the kidney.

Heredity  Plays a role in the development of cancer.  Some persons are characterized by inheritance of single mutant genes that greatly increase the risk of developing a tumour, e.g. familial retinoblastoma familial adenomatous polyposis.

Acquired pre-neoplastic disorders: Certain clinical conditions are associated with an increased risk of developing cancers.  Cirrhosis of the liver will lead to hepatocellular carcinoma.  Chronic atrophic gastritis will lead to stomach cancer.  Chronic ulcerative colitis will lead to carcinoma of the colon.  Leukoplakia of the oral and genital mucosa will lead to squamous cell carcinoma.

Hyperplastic and dysplastic proliferations: e.g.  Atypical endometrial hyperplasia leads to endometrial carcinoma.  Dysplastic bronchial mucosa of habitual cigarette smokers leads to bronchogenic carcinoma.  Villous adenoma of the rectum leads to colorectal carcinoma.

Problems associated with malignancies  1- Anemia:  2- Loss of function:  3-Malnutrition and cachexia:  4- Infections:  5-Paraneoplastic syndromes:

Problems associated with malignancies 1- Anemia: It is due to :  Chronic blood loss (usually, associated with gastrointestinal or genitourinary neoplasms), symptoms of cancer such as weakness and fatigue.  Poor nutrition especially in oral and esophageal cancers  Metastatic replacement of the red-cell producing bone marrow.

 2- Loss of function: can result from the mass effect of cancer or from replacement of normal tissue.  3-Malnutrition and cachexia: Cachexia: is defined as a state of general weakness, wasting and loss of body fat.

Malnutrition is due :  Loss of appetite especially noticed in cancer of head and neck or upper gastrointestinal tract.  Nausea and vomiting resulting from radiotherapy and/or chemotherapy.  Carcinoma may produce substances that interfere with intestinal absorption or produce diarrhea.  Proteoglycans that cause breakdown of skeletal muscle proteins have been detected in the urine of cancer patients.

4- Infections: Due to:  Obstructive neoplasms which cause obstruction of a bronchus leading to post-obstructive infection such as bronchiectasis and/or pneumonia.  Altered host resistance may permit relatively avirulent organisms e.g. normal bacterial flora, as well as common viruses and fungi to cause infection and death

 5-Paraneoplastic syndromes: Definition Symptom complexes seen in cancer patients. These symptoms are neither caused by the tumour itself nor by its metastases or by hormones secreted by the tumour tissue of origin, but it is due to ectopic hormonal production e.g. ACTH (adrenocorticotropic hormone)may be increased in some forms of lung cancer leading to Cushing's syndrome that may be a life threatening clinical problem.

Laboratory Diagnosis of cancer 1- Histologic methods: histologic examination is the most important method of diagnosis 2-Cytologic methods:  I-Fine needle aspiration  II- Cytologic Papanicolaou smears

3- Tumour markers:  Tumour-derived associated molecules that can be detected in the blood.  They are not primary methods of diagnosis, but rather adjuvant to the diagnosis.  They may be of value in determining the response to therapy or the occurrence of tumour recurrences.

 Alpha-fetoprotein (a-FP): a-fetoprotein is a substance normally produced by fetal yolk sac and developing embryonic liver cells but not by normal adult cells or tissue. Measurement of a- FP level is useful in indicating the presence of liver or testicular cancer, and in assessing tumour recurrence and response to therapy.  Assay of serum levels of prostatic specific antigen (PSA) has been used in the diagnosis of early carcinoma of the prostate, and in monitoring patients for recurrent or progressive disease.