1.What is Cancer?

Cancer is a group of diseases which arises from a single mutation resulting in uncontrolled cell proliferation and spread (metastasis) to nearby tissue or secondary organs. The abnormal mass of cells is termed as tumor or neoplasm. The tumor is benign when the cells are not invasive. When the cells become capable of invading the surrounding tissue, it is called malignant, i.e., cancer.

Cancer can be treated by surgery, that is, removing tumor when it is in the benign stage. Chemotherapy is used to kill cancerous cells. It includes intravenous injection, cream or ointment, oral drugs (liquid, capsule, and tablet). Radiation is used alone or with the combination of surgery or chemotherapy. Other treatments include immunotherapy (use of cytokine, antibody), hormonal therapy, stem cell transplants.

About 30-50% of cancer can be prevented by improving lifestyle, avoiding tobacco or alcohol, and raising awareness about infection, exposure to carcinogens and environmental pollution.

2. What are the causes of cancer?

Carcinogenesis is the development of cancer and the substances causing cancer are referred to as carcinogens. The external agents responsible for cancer are categorized as-

• Physical carcinogens- radiation such as X-ray, UV-ray which causes chromosomal breakage, DNA alterations.

• Chemical carcinogens- ethidium bromide, asbestos, arsenic, components of tobacco smoke etc. Tobacco use is the most important risk factor comprising 22% deaths.

• Biological carcinogens- infections from certain viruses, bacteria and parasites. Viral infections including papillomavirus, hepatitis-B & C virus, Epstein- Barr virus, HIV and others are responsible for one-fourth death cases.

Other risk factors are-

• Obesity

• Poor diet

• Lack of exercise

• Excessive drinking

• Several disease complications

• Epigenetic change

• Heredity or family history of genetic defects (5-10% cases).

Not a single cause accounts for the development of cancer, rather it is a multistep process where multiple factors contribute to its progression.

Diagnosis is important to understand the specific type of cancer so that the treatment becomes easier and lives can be saved. Laboratory test (blood test, urine/feces test), endoscopy (visual examination of the interior of a hollow body organ), tumor biopsy (physical examination of tissue or body fluid) and imaging are performed to diagnose cancer.

3. Cancer Types

According to the tissue of origin, types of cancers are-

1. Carcinoma (arising from epithelial cells)

2. Sarcoma (developed from connective tissue or muscle cells)

3. Melanoma (derived from skin pigment)

4. Leukemia (cancers of white blood cells)

5. Lymphoma & Myeloma (originated from immune cells)

More than 100 types of cancers are classified according to the organs involved (WHO, 2018). The most common are-

1. Lung cancer (2.09 million cases)

2. Breast cancer (2.09 million cases)

3. Colorectal cancer (1.80 million cases)

4. Prostate cancer (1.28 million cases)

5. Skin cancer (non-melanoma) (1.04 million cases)

6. Stomach cancer (1.03 million cases)