RESPIRATORY - Lung Cancer Midterm Notes PDF

4 1 RESPIRATORY – Lung Cancer Lung Cancer Lung cancer is one of the most common and deadliest cancers globally. It can be classified into two major types: 1. Non-Small Cell Lung Cancer (NSCLC) – Account...

4 1 RESPIRATORY – Lung Cancer Lung Cancer Lung cancer is one of the most common and deadliest cancers globally. It can be classified into two major types: 1. Non-Small Cell Lung Cancer (NSCLC) – Accounts for about 85% of all lung cancers. o Adenocarcinoma (35-40%) o Squamous cell carcinoma (30%) o Large-cell carcinoma (10%). 2. Small Cell Lung Cancer (SCLC) – Accounts for about 15% of lung cancers, but is responsible for 25% of lung cancer deaths due to its aggressive nature and early metastasis. 1. Most Likely Cause Cause: o Smoking: Tobacco smoke is the most common cause of lung cancer. It contains a large number of carcinogens that induce geneLc mutaLons, such as mutaLons in the p53 tumor suppressor gene. o GeneHc MutaHons: AcLvaLon of oncogenes (like EGFR and KRAS) and loss of tumor suppressor genes (like p53) are major molecular drivers. o OccupaHonal Exposures: Exposure to asbestos, arsenic, chromium, nickel, and ionizing radiaLon increases the risk. o Air PolluHon: ParLculate maQer (PM2.5) and other air pollutants contribute to lung cancer development【105:0†source】. o Other Causes: Family history and geneHc predisposiHons can increase the likelihood of developing lung cancer. 2. Pathophysiology The pathophysiology of lung cancer is complex and involves a series of mutaLons that transform normal epithelial cells into malignant ones. 1. MutaHon of Genes: o Oncogene acLvaLon (EGFR, KRAS) and loss of tumor suppressor genes (p53, RB1) drive uncontrolled cell division. o Cells evade apoptosis, leading to immortalizaHon of cancer cells. 2. Uncontrolled Cell Growth: o Squamous Cell Carcinoma: Typically begins in the central bronchi. It grows slowly but can lead to airway obstrucHon, causing a non-producHve cough or hemoptysis. o Adenocarcinoma: Arises in peripheral lung Hssue and is linked to geneLc mutaLons in EGFR, oWen in non-smokers. o Large Cell Carcinoma: Composed of undifferenHated cells, it arises centrally and grows rapidly, leading to poor prognosis. o Small Cell Lung Cancer (SCLC): Arises from neuroendocrine cells and spreads rapidly. It can lead to paraneoplasHc syndromes, such as SIADH (syndrome of  2 inappropriate anLdiureLc hormone) and Cushing’s syndrome (due to ectopic ACTH producLon). 3. Angiogenesis and Metastasis: o Cancer cells induce angiogenesis to secure a blood supply. o Metastasis occurs as cancer cells break away and spread to lymph nodes, brain, liver, and bones. 3. Disease Transmission Transmission: o Not transmissible. Lung cancer is a non-infecHous disease. o No human-to-human transmission occurs. o Risk factors, such as second-hand smoke exposure, increase suscepLbility, but the disease is not "transmiQed" like an infecLon. 4. Risk Factors Risk factors for lung cancer can be divided into modifiable and non-modifiable factors. Modifiable Risk Factors Smoking: Most important risk factor. It accounts for 80-90% of lung cancer cases. Secondhand Smoke: Prolonged exposure increases the risk. OccupaHonal Hazards: Exposure to asbestos, arsenic, nickel, and ionizing radiaHon increases lung cancer risk. Air PolluHon: Prolonged exposure to parHculate maaer (PM2.5) increases the risk. Radon Gas: Radon is a naturally occurring radioacLve gas that can accumulate in poorly venLlated areas. Non-Modifiable Risk Factors Age: The risk of lung cancer increases with age. GeneHc Factors: Family history of lung cancer increases the likelihood of developing it. Gene MutaHons: Variants in genes like CYP1A1 and p53 are linked to lung cancer development. Summary Table Criteria Lung Cancer Most Likely Smoking (primary cause), occupaLonal exposure (asbestos, arsenic), air Cause polluLon, radon gas exposure, family history, geneLc mutaLons (EGFR, p53). Gene mutaLons (p53, EGFR), oncogene acLvaLon, tumor formaLon. Subtypes: Squamous Cell Carcinoma (central, slow growth), Pathophysiology Adenocarcinoma (peripheral, metastasizes early), Large-Cell Carcinoma (undifferenLated, rapid growth), and Small Cell Lung Cancer (SCLC) (neuroendocrine, paraneoplasLc syndromes). Transmission Not transmissible. Lung cancer is non-infecLous. Modifiable: Smoking, secondhand smoke, occupaLonal hazards, air Risk Factors polluLon, radon exposure. Non-Modifiable: Age, geneLc predisposiLon, mutaLons in p53, CYP1A1.  3 Clinical Features of Lung Cancer Symptoms: o Cough (persistent, non-producLve) – OWen associated with squamous cell carcinoma. o Hemoptysis (coughing up blood) – Due to airway invasion. o Shortness of Breath (Dyspnea) – Caused by tumor-related airway obstrucHon. o Weight Loss – OWen seen in late stages. o ParaneoplasHc Syndromes – Seen in SCLC: § SIADH: Water retenLon, hyponatremia. § Cushing’s Syndrome: Increased corLsol due to ectopic ACTH secreLon. § Eaton-Lambert Syndrome: Neuromuscular disorder caused by anLbodies against presynapLc calcium channels.