What is Cancer?
It’s not just a single disease, but a cluster of disease causing uncontrolled proliferation of abnormal body cells! Cancer is characterized by out –of-control or manic cell growth forming lumps or masses of cells/tissues or tumours which either stay and grow and spread to other parts of the body affecting distant tissues or organs.
Formation of tumour is not an easy or quick process; numerous body’s natural defense mechanism have to fail to produce a single tumour cell. Neoplasm or tumour is formed when there is an abnormal growth of a tissue in the body via tumour initiation process. If a tumour stays small and confined to a particular area, it is termed as benign tumour (like mole or uterine fibroids) and it lacks the ability to invadeor affect other body parts. Being non- cancerous, they grow very slowly and rarely cause any serious complications or threaten life unless are located in a vital organ(like main artery or brain), grow very large or press neighboring tissues. Our immune system separates these tumour cells from rest of the body cells by placing them in a sac like structure.
However, when some of the benign tumours undergo tumour progression process wherein various factors permit the benign cancer cell to survive and expand in number, precancerous cells are formed. These cells then defeat activities of tumour suppressor genes(apoptosis) and come under direct influence of oncogenes, and if left untreated /undetected, become the aggressive type of tumour , called malignant tumour. These cells have invasive properties and metastasize (spread) to various body parts. They keep proliferating uncontrollably, causing phenotypical and anatomical changes, while destroying the health body cells, forming cancer.
Cancer- Types and Causes:
There is no single well- defined casual factor that exists for cancer and various factors contribute to its onset and development. It’s a disease wherein things go wrong at the genetic level unlike a fever or fracture.
- Proto- Oncogenes- These genes normally control or trigger division in cell when they are scheduled to divide and decide the degree of differentiation. Mutations in these lead to formation of oncogenes that cause uncontrolled cell growth.
- Tumour suppressor genes- These genes notify cells when not to divide and stop cell division along with regulating cell death. Once these are mutated, an out of control cell growth can cause cancer.
- Suicide Genes- Mediate destruction of cells in case of mutation and if these are mutated, cells do not die but keep on dividing, passing in the mutation to daughter cells.
- DNA-repair genes- Repair any damaged DNA in cells, and when they are mutated, they are unable to correct the mutations in body cell’s genome which give rise to cancerous cells.
Carcinogens– Substances whose sudden or prolonged presence or exposure, can cause a mutation in a normal gene(s), damaging DNA, altering its function and metabolism, are known as carcinogens.
- Chemical carcinogens: Theses include substances like organic compounds, mineral, substances like food carcinogens, tobacco, asbestos, exhaust fumes of automobiles, arsenic, etc. which lead to formation of free radicals damaging healthy cells, affecting their function.
- Physical carcinogens: Depending on the length of exposure, these rays can penetrate the skin and mainly cause radiation induced cancers via ionizing radiations (X-rays, gamma rays) and non-ionizing radiations(ultraviolet radiations-UVB, infrared radiation).
- Biological carcinogens: These include natural compounds or contaminants from plants like nicotine, reserpine, Streptomyces, etc. to which humans are indirectly exposed upon consumption of milk m meat and secondary products from animals feeding in plants. Animal carcinogens include those produced by insects(quinones), certain parasite toxins(trematodes), etc.
- Oncogenic Viruses: These infections organisms transform morphological and biochemical characteristics of host cells by incorporating and integrating their genetic material(DNAor RNA) in the host’s DNA. E.g: Hepatitis B or C viruses can cause liver cancer, Epstein- Barr viruses can cause non-Hodgkin lymphomas and nasopharyngeal cancer, etc.
Major Cancer Types:
- Carcinoma- The cancer begins in the epithelial cells, affecting the tissues lining the inner or outer surfaces of the body. E.g. cancers of lung, colon, appendix, cervix, and urinary bladder, etc.
- Sarcoma- This type of cancer develops from the cells originating in mesenchymal cells outside the bones marrow, i.e. from the connective tissues ( cartilage, fat, muscles, nerves and bones).
- Lymphoma- A type of blood cell tumour, which originates in the lymph nodes and immune system tissues.
- Leukemia- Starts in the bone marrow, it leads to production of high numbers of abnormal white blood cells which accumulate in the blood stream.
- Adenoma- Mostly a benign tumour of epithelial tissues of glandular origin and characteristics, it can affect colon renal, adrenal, thyroid. Pituitary, parathyroid, liver, breast, appendix, bronchial, sebaceous, salivary glands, prostate, etc.
Does Cancer strike with signs?
Cancer cell masses can stay asymptomatic for longer duration showing less serious but perturbing physiological symptoms like,
- Changes in bowel or bladder habits
- Thickened lump in breast, testicles or other body parts
- Visible changes in size , colour, thickness or shape of a mole or wart
- Persistent sore throat, nagging hoarseness or cough
- Difficulty swallowing and chronic indigestion
- Unexplained low-grade fevers(either persistent or recurrent)
- Unexplained weight and appetite loss
- Persistent fatigue and vomiting
- Unusual discharged or bleeding
- Continuous pain in bones or other parts
- Skin changes
- Delayed healing of sores
- White patches inside mouth or white spots on the tongue
- Recurring infections not cleared by usual treatment
Diagnosis: Once cancer is suspected, a patient and familial medical history along with a thorough physical examination is performed. A specialist will carry out following investigations prior to making a diagnosis.
Laboratory Tests: Certain biochemical analyses of blood urine, or other body fluids that measure presence or elevated levels of tumour markers can aid in diagnosing a particular cancer type. For e.g. Complete blood count can show the presence of unusual numbers or type of white blood cells indicating leukemia. The result do not indicate a definitive diagnosis, as following imaging tests are must to confirm a tumour.
Imaging Tests: Positron Emission Tomography- Computed Tomography (PET-CT) scan: A radioactive tracer is injected into the blood stream which gets incorporated in the body tissues. Combining the technologies of both PET and CT, this scan reveals structural and functional information of body’s cells and tissues in a single imaging session,. This painless procedure can visualize cancerous cells and the rate at which they take up glucose to determine the tumour grade.
X- rays: Low doses of electromagnetic radiation create images of structures inside the body that help detect and stage tumour.
Computerized Tomography (CT) scan: Using X-ray equipment linked to a computer , thus scan aids in detecting abnormal growths and stages of cancer. Further, these scans can suide a biopsy procedure, treatments like cryotherapy, planning external- beam radiation therapy or surgery, determination whether a cancer is responding to treatment and to detect recurrence of a tumour.
Magnetic Resonance Imaging (MRI) Scan: Using radiofrequency waves with magnetic field creates detailed cross-sectional images of inside of the body which are visible on a computer. This scan can distinguish between normal and cancerous tissues, precisely revealing metastases with a greater contrast within soft tissues as compared to a CT scan, thus playing a crucial role in cancer staging and treatment.
Bone Scintigraphy: Patient is injected with a radiotracer ( mostly Tc with methylene diphosphonate) and areas with too much or too little absorbed tracer indicate bone inflammation and cancer.
Ultrasound: Sound waves are projected to the body which generate echoes off abnormal tissue differently than those of a healthy tissue, to create picture of these areas (tissue or organs). This test distinguishes tumours from normal cells and marks out boundaries of a tumour prior to its removal.
Biopsy Studies: It is an examination of affected tissue by extracting it from the body using a needle (fine- needle aspiration cytology-FNAC), endoscope or surgery to detect the presence , cause or extent of ac cancer type. Common biopsy sites w.r.t cancer type include breast, skin, gastrointestinal tract, lung, bladder, liver, colon, bone marrow and lymph nodes.
Other tests include mammograms, PAP test, thyroid scans, Gallium scans, etc.
Treatment: Based on the diagnosis, cancer is staged(location, size, type of tumour is determined) and various treatment modalities are prescribed starting with primary treatment(to completely remove cancer cells from body via surgery, radiation therapy or chemotherapy), fooled by adjuvant treatment (to reduce chances of cancer’s recurrence via chemotherapy, immunotherapy, radiation therapy and hormone therapy) and palliative treatment ( to relieve side effect of treatment or signs and symptoms caused by cancer via targeted drug therapy, surgery, radiation, chemotherapy and hormone therapy). Cancer is curable if detected early and with the above mentioned treatment modalities, can be cured, reducing the spread and damage. Sometimes, cancer cells remain in the body for years and often go unnoticed even post treatment. To detect cancer recurrence, regular follow up testing is indispensable.