Cancer — Revision Notes

⚡ 30-Second Revision

Cancer — Uncontrolled cell growth & division.
Tumor — Abnormal mass of cells.
Benign — Localized, non-invasive, non-metastatic.
Malignant — Invasive, metastatic, cancerous.
Metastasis — Spread of cancer cells to distant sites.
Proto-oncogenes — Promote normal cell growth; mutate to oncogenes (accelerator 'on').
Tumor Suppressor Genes — Inhibit cell growth; inactivation leads to uncontrolled growth (brakes 'off').
Carcinogens — Cancer-causing agents (Physical: UV, X-rays; Chemical: Tobacco, Asbestos; Biological: HPV, HBV).
Detection — Biopsy (definitive), Imaging (CT, MRI), Blood tests (markers).
Treatment — Surgery, Radiotherapy, Chemotherapy, Immunotherapy, Targeted Therapy.
Chemotherapy Side Effects — Hair loss, nausea, fatigue (due to targeting rapidly dividing healthy cells).

2-Minute Revision

Cancer is a disease of uncontrolled cell proliferation, leading to tumors. It's caused by genetic mutations in genes regulating the cell cycle. Proto-oncogenes normally promote growth but become oncogenes when mutated, driving uncontrolled division.

Tumor suppressor genes normally inhibit growth; their inactivation removes the 'brakes.' Malignant tumors are cancerous, characterized by invasion of surrounding tissues and metastasis (spread to distant sites), unlike benign tumors which are localized.

Carcinogens, including physical (UV, X-rays), chemical (tobacco, asbestos), and biological (HPV, HBV) agents, induce these mutations. Early detection is vital, primarily through biopsy and histopathological examination, supported by imaging (CT, MRI).

Treatment involves a combination of surgery (removal), radiotherapy (radiation to kill cells), chemotherapy (drugs killing rapidly dividing cells, causing systemic side effects like hair loss and nausea), and newer immunotherapy and targeted therapy approaches.

Understanding these core concepts and distinctions is key for NEET.

5-Minute Revision

Cancer is a complex disease marked by uncontrolled cell growth and division, forming abnormal masses called tumors. This cellular anarchy stems from accumulated genetic mutations that disrupt the delicate balance of the cell cycle.

Key players in this disruption are proto-oncogenes, which normally promote cell growth but, when mutated, become oncogenes (like a stuck accelerator pedal), driving continuous proliferation. Conversely, tumor suppressor genes (like the brakes, e.

g., p53) normally halt growth and repair DNA; their inactivation allows damaged cells to divide unchecked.

The critical distinction for NEET is between benign and malignant tumors. Benign tumors are non-cancerous, localized, encapsulated, and do not spread. Malignant tumors, however, are cancerous, grow rapidly, invade surrounding tissues, and crucially, can undergo metastasis – where cells break off and spread to distant organs, forming secondary tumors. This metastatic potential is what makes cancer so dangerous.

Cancer development is often triggered by carcinogens:

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Physical — Ionizing radiation (X-rays, gamma rays) and non-ionizing radiation (UV rays, causing skin cancer).
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Chemical — Tobacco smoke (lung, oral cancer), asbestos (mesothelioma), certain industrial chemicals.
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Biological — Oncogenic viruses like Human Papillomavirus (HPV, causing cervical cancer) and Hepatitis B/C viruses (liver cancer).

Detection relies heavily on biopsy and histopathological examination for definitive diagnosis. Imaging techniques like CT, MRI, and PET scans help locate tumors and assess spread. Blood tests for tumor markers can also be indicative.

Treatment is often multimodal:

Surgery — Physical removal of localized tumors.
Radiotherapy — Uses high-energy radiation to damage cancer cell DNA, often localized.
Chemotherapy — Systemic drugs that kill rapidly dividing cells. While effective against widespread cancer, it causes side effects (hair loss, nausea, fatigue) by affecting rapidly dividing healthy cells.
Immunotherapy — Boosts the body's immune system to fight cancer.
Targeted Therapy — Drugs that specifically attack cancer cells' unique molecular vulnerabilities.

Remember the hallmarks of cancer: sustained proliferation, evasion of growth suppressors, resistance to cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis.

Prelims Revision Notes

Cancer: The Basics

Definition — Uncontrolled, abnormal cell growth and division.
Tumor — Mass of abnormal cells.
Types of Tumors

* Benign: Non-cancerous, localized, encapsulated, non-invasive, non-metastatic, generally not life-threatening. Cells are well-differentiated. * Malignant: Cancerous, rapid growth, invasive, capable of metastasis (spread to distant sites via blood/lymph), life-threatening. Cells are poorly differentiated/anaplastic.

Genetic Basis of Cancer

Proto-oncogenes — Normal genes promoting cell growth. Mutations convert them to oncogenes (gain-of-function, like accelerator stuck 'on').
Tumor Suppressor Genes — Genes inhibiting cell growth, repairing DNA, inducing apoptosis (e.g., p53, Rb). Inactivation (loss-of-function, like brakes 'off') leads to uncontrolled growth.
Cancer often requires mutations in both types of genes.

Carcinogens (Cancer-Causing Agents)

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Physical Carcinogens

* Ionizing radiation: X-rays, gamma rays (cause DNA damage). * Non-ionizing radiation: UV rays (cause DNA damage, leading to skin cancers like melanoma).

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Chemical Carcinogens

* Tobacco smoke: Contains polycyclic aromatic hydrocarbons (lung, oral, throat, bladder cancers). * Asbestos: (Mesothelioma, lung cancer). * Benzene: (Leukemia). * Certain dyes, pesticides.

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Biological Carcinogens

* Oncogenic viruses: * Human Papillomavirus (HPV): Cervical cancer. * Hepatitis B Virus (HBV) & Hepatitis C Virus (HCV): Liver cancer. * Epstein-Barr Virus (EBV): Burkitt's lymphoma. * Bacteria: *Helicobacter pylori* (stomach cancer).

Cancer Detection and Diagnosis

Biopsy and Histopathological Examination — Definitive diagnostic method. Tissue sample examined under microscope.
Imaging Techniques

* Radiography (X-rays) * Computed Tomography (CT scan) * Magnetic Resonance Imaging (MRI) * Positron Emission Tomography (PET scan) * Used to detect tumors, assess size, and check for metastasis.

Blood/Bone Marrow Tests — For leukemias.
Tumor Markers — Blood tests for specific substances (e.g., PSA for prostate cancer), used for screening/monitoring, not definitive diagnosis.

Cancer Treatment

Surgery — Removal of localized tumors.
Radiotherapy — High-energy radiation to kill cancer cells. Localized effects.
Chemotherapy — Systemic drugs killing rapidly dividing cells.

* Side Effects: Hair loss, nausea, fatigue, anemia, immunosuppression (due to damage to rapidly dividing healthy cells like hair follicles, GI lining, bone marrow).

Immunotherapy — Boosts patient's immune system to fight cancer.
Targeted Therapy — Drugs specifically target molecular pathways in cancer cells.
Hormone Therapy — For hormone-sensitive cancers.
Often, a combination of therapies is used.

Vyyuha Quick Recall

To remember the key characteristics of Malignant tumors (the dangerous ones), think of M.I.N.T.S.:

Metastasis (Spreads to distant sites)
Invasive (Invades surrounding tissues)
No encapsulation (Lacks a fibrous capsule)
Tumor angiogenesis (Induces new blood vessel formation)
Sustained proliferation (Uncontrolled growth)