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Oncology-Predictive Genetic Testing
I. Predictive Genetic Testing: The Basics
  • Purpose: To determine if a family member has inherited a specific gene mutation known to increase cancer risk. This is offered after a mutation is identified in a family member and they consent to share their results.
  • Process: Typically conducted through a clinical genetics service, preceded by genetic counseling to fully explain the implications.
  • Result Interpretation:
    • Positive Result: Does not guarantee cancer development, but informs surveillance needs and risk-reducing surgery decisions. It also clarifies risks for future generations.
    • Negative Result: Does not guarantee against cancer development. It simply means the specific familial mutation wasn't found; a genetic predisposition may still exist.
  • Considerations: Psychological distress for the individual being tested and their family should be anticipated and addressed. Potential insurance implications are also a concern, although guidelines exist to mitigate these in many regions.
II. Implications for the Affected Individual (Whose Sample Initiates Testing)
The focus on predictive testing often overlooks the implications for the affected individual whose genetic material initiates the testing process. These implications include:
  • Negative Test Results: A negative result (no mutation identified) does not rule out a genetic predisposition in the family. It simply means the specific mutation causing cancer in the family hasn't been found yet. More research may be needed to discover the underlying genetic cause.
  • Uncertain Test Results: Sometimes a "sequence change" is found but its significance (benign or pathogenic) is unclear. Further testing is often required for clarification.
  • Positive Test Results: A positive result can lead to:
    • Psychological Distress: Including guilt over potentially passing the mutation to family members, especially children.
    • Increased Cancer Risks: Identifying a specific mutation might reveal a heightened risk for other cancers (e.g., ovarian cancer with a BRCA1 breast cancer mutation) not initially apparent from the family history (metachronous cancers or cancers at associated sites).
III. Key Concepts to Remember
  • No guarantees: Neither positive nor negative predictive genetic testing results guarantee the development or absence of cancer.
  • Psychological impact: The emotional consequences for the tested individual and their family must be carefully considered.
  • Further investigation: Negative or unclear results may require additional testing or research.
  • Broader implications: Testing results can significantly impact medical decisions, family planning, and insurance


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Oncology -Bowel Cancer Family History

I. Recognizable Syndromes & Polyposis:
  • Increased risk can stem from identifiable syndromes characterized by polyp presence.
  • Genetic testing is effective in identifying causative mutations in most cases.
  • Key Syndromes & Polyposis:
    • FAP (Familial Adenomatous Polyposis): Classically >100 bowel polyps. Autosomal dominant; mutations in the same gene as attenuated FAP, differing in mutation site and phenotype.
    • Attenuated FAP: <100 polyps, later onset, high bowel cancer risk, and risk for upper gi malignancy. autosomal dominant, same gene as fap.< />pan>
    • MYH-associated polyposis: Autosomal recessive; predisposition to adenomatous bowel polyps; often presents with sibling history of bowel cancer. Testing focuses on two common MYH gene mutations.
II. Hereditary Non-Polyposis Colon Cancer (HNPCC) / Lynch Syndrome:
  • More common than recognizable syndromes.
  • Characterized by: Familial aggregation of bowel cancer with fewer polyps.
  • Genetic basis: Primarily due to mutations in mismatch repair genes (MLH1, MSH2, MSH6, PMS2). Defective DNA repair leads to increased mutation rates and faster cancer progression.
  • Microsatellite instability (MSI): A laboratory finding in tumor tissue indicating a likely mismatch repair gene mutation. Used in risk assessment.
III. Risk Assessment & Management:
  • Family History Assessment: Crucial for determining risk level. Factors considered:
    • Low Risk: One affected relative >45 years; two relatives >55 years or on different sides of the family. Reassurance may be appropriate.
    • Moderate Risk: One relative <45 years; two relatives (one <55 years); three affected at any age. tumor tissue analysis is warranted.< />pan>
    • High Risk (Amsterdam Criteria): At least three individuals with bowel cancer across two generations; at least one affected individual <50 years; familial polyposis excluded.< />pan>
  • Tumor Tissue Analysis (for moderate risk):
    • MSI testing: Identifies potential mismatch repair gene mutations.
    • Loss of expression of mismatch repair proteins: Helps determine which gene to analyze first.
    • BRAF V600E mutation testing: Its presence suggests sporadic cancer (not germline mutation) and hypermethylation.
  • Genetic Testing: Offered if mutation suspected (moderate or high risk). Guides surveillance strategies.
  • Surveillance Strategies:
    • Moderate risk: Colonoscopy at presentation and at age 55.
    • High risk (known gene carriers): 2-yearly colonoscopies from age 25 or 35 (depending on family history).
  • Additional Considerations: Families with known mismatch repair gene mutations should also consider surveillance for endometrial cancer (high risk) and other cancers (e.g., gastric cancer in those >50).
IV. Key Terms & Concepts:
  • Autosomal Dominant: One affected allele leads to the condition.
  • Autosomal Recessive: Two affected alleles are required.
  • Mismatch Repair Genes: Genes involved in DNA repair; mutations increase cancer risk.
  • Microsatellite Instability (MSI): A marker of mismatch repair deficiency.
  • Germline Mutation: A mutation present in all cells of the body, inherited from parents.
  • Somatic Mutation: A mutation acquired during an individual's lifetime, not heritable.
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Oncology-Low-Risk Alleles and Cancer Risk
I. Key Concepts:
  • Genome-Wide Association Studies (GWAS): Large-scale studies that scan the entire genome to identify genetic variations (SNPs) associated with a particular disease. They're crucial for identifying low-risk alleles.
  • Single Nucleotide Polymorphisms (SNPs): Single base-pair variations in DNA sequence. These are the most common type of genetic variation and can occur anywhere in the genome, including promoter regions (affecting gene expression) and introns (non-coding regions).
  • Low-risk alleles: SNPs identified through GWAS that individually contribute a small increase in disease risk. Crucially, their cumulative effect can significantly impact disease development.
  • Oncogenes and Tumor Suppressor Genes: Genes that, when mutated, can contribute to cancer development. Oncogenes promote cell growth, while tumor suppressor genes inhibit it.
  • Genetically Engineered Mouse Models (GEMMs): Mice genetically modified to mimic human diseases, allowing researchers to study disease mechanisms and test therapeutic strategies.
II. Low-Risk Alleles and Colon Cancer:
The text focuses on the discovery of low-risk alleles for colon cancer via GWAS. These SNPs are frequently located in:
  • Promoter regions: Affecting gene expression levels of key genes.
  • Introns: Although not directly coding for proteins, introns can impact gene expression through regulatory mechanisms.
Importantly, these SNPs are often found within established cancer pathways:
  • MYC oncogene: An oncogene whose over-expression is implicated in many cancers.
  • Bone Morphogenetic Protein (BMP) signaling pathway: A crucial pathway involved in cell growth and differentiation; disruption can lead to uncontrolled cell growth.
III. Significance of Low-Risk Alleles:
The use of GEMMs is crucial in demonstrating the impact of these seemingly insignificant low-risk alleles. Manipulating these SNPs in GEMMs has shown profound effects on tumor development, suggesting that even small genetic variations can contribute substantially to cancer initiation and progression.
IV. Clinical Implications:
The discovery of disease-associated SNPs, even low-risk ones, holds important clinical implications. Individuals carrying these SNPs may require:
  • Increased screening: More frequent colonoscopies or other screening methods to detect cancer early.
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Oncology- Multidisciplinary Approach to Cancer Management
This guide summarizes the complexities of cancer treatment and the crucial role of multidisciplinary teams (MDTs).
I. Core Concept: The Need for a Multidisciplinary Approach
Cancer treatment is highly complex, requiring diverse expertise beyond the scope of any single clinician. This necessitates a multidisciplinary team (MDT) approach. No one specialist possesses the full range of skills for diagnosis, staging, treatment (surgery, chemotherapy, radiotherapy, hormonal therapy), and long-term care needed across various cancer types.
II. Key Components of Cancer Management:
  • Diagnosis & Staging: Initial assessment involves various diagnostic tests (pathological confirmation and imaging) to determine the cancer type and extent of its spread.
  • Surgical Intervention: Surgery is frequently a primary treatment modality.
  • Adjuvant Therapies: These therapies complement surgery, including chemotherapy, radiotherapy, and hormonal therapy. These are often used pre- or post-operatively.
  • Palliative Care: This specialized care focuses on improving quality of life for patients with advanced cancer. It may be integrated at various stages of the illness.
III. The Role of the Multidisciplinary Team (MDT):
MDTs are composed of a range of healthcare professionals, including but not limited to: surgeons, oncologists, radiotherapists, nurses, physiotherapists, stoma nurses, counselors, and palliative care specialists. The specific composition varies depending on the institution and the type of cancer being treated.
The MDT's responsibilities encompass several key areas:
  • Treatment Planning: Collaborative decision-making regarding diagnostic procedures, primary treatment strategies (including surgery, radiotherapy and chemotherapy), and adjuvant therapies.
  • Patient Preparation: Physically and psychologically preparing patients for treatment and follow-up. This includes providing comprehensive information about the treatment process, prognosis, potential side effects, and any necessary post-treatment care (e.g., stoma care).
  • Treatment Delivery: Efficient coordination and execution of surgery, radiotherapy, and chemotherapy.
  • Rehabilitation & Follow-up: Providing rehabilitation services and ongoing monitoring post-treatment.
  • Palliative Care Integration: Seamless transition to palliative care when appropriate.
  • Clinical Trial Participation: Encouraging patients to consider participating in relevant clinical trials.
  • Quality Assurance: The MDT actively audits its procedures and performance to ensure continuous improvement and benchmarking against other teams.​
IV. Benefits of the MDT Approach:
Studies show MDT management leads to improved patient outcomes:
  • Increased Survival Rates: Improved survival times are a key benefit.
  • Enhanced Quality of Life (QoL): Patients experience improvements in physical functioning, psychological well-being, and cosmetic outcomes, contributing to a better overall QoL.
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Oncology-Oncology Surgical Principles
This guide summarizes key concepts regarding the surgical management of solid tumors. Focus on understanding the nuances, not just memorizing facts.
I. General Principles of Surgical Oncology:
  • Surgery's Central Role: Surgery remains the primary treatment and offers the best chance of cure for most solid tumors, particularly those localized. However, advancements allow for long-term survival even in some metastatic cases.
  • Five Main Surgical Roles: Grasp the distinct roles surgery plays:
    • Diagnosis & Staging: Surgical biopsy for definitive diagnosis and assessing tumor extent.
    • Curative Surgery: Removal of the entire tumor with the aim of a complete cure.
    • Palliative Surgery: To alleviate symptoms and improve quality of life, not necessarily to cure.
    • Surgery for Metastatic Disease: Addressing spread of cancer, e.g., removing metastases.
    • Prophylactic Surgery: Preventive surgery to reduce cancer risk (e.g., mastectomy in high-risk individuals).
  • Tumor Biology is Crucial: Surgical planning necessitates a deep understanding of the tumor's biology and behavior. Failure to account for this leads to poor outcomes.
II. Tumor Spread & Implications for Surgery:
  • Three Main Spread Mechanisms: Understand the differences in spread and their surgical implications.
    • Direct Infiltration: Tumor grows into adjacent tissues.
    • Lymphatic Spread: Cancer cells travel through the lymphatic system.
    • Blood-borne Spread (Hematogenous): Cancer cells spread via the bloodstream.
  • Variability in Spread Patterns: Most cancers utilize all three mechanisms, but to varying degrees. Recognize these examples:
    • Breast & Colorectal Cancers: Primarily lymphatic and hematogenous spread.
    • Upper GI & Upper Airway Cancers: Predominantly lymphatic spread.
    • Thyroid Cancer (Papillary vs. Follicular): Illustrates how even cancers of the same origin can spread differently (lymphatic vs. hematogenous, respectively). This directly impacts surgical approach.
III. Tumor-Host Interaction:
  • Inflammation's Importance: The interplay between the tumor and the host's inflammatory response is increasingly recognized as crucial for predicting outcome and guiding adjuvant therapy decisions. This is an area of active research.​



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Oncology-Diagnosis and Staging of Malignant Disease
This guide summarizes techniques for diagnosing and staging malignant diseases, emphasizing best practices and potential pitfalls.
I. Improving Diagnostic Accuracy:
  • Advanced Imaging: Ultrasound, CT, and MRI significantly improve localization and staging, guiding more accurate biopsies.
  • Biopsy Techniques:
    • Fine Needle Aspiration (FNA) Cytology: Less invasive, but may yield insufficient tissue for complete analysis. Lower risk of tumor seeding than core biopsy.
    • Core Biopsy: Preferred for adequate tissue architecture and receptor status assessment (e.g., breast cancer). Higher risk of tumor seeding than FNA.
    • Endoscopic Techniques (including EUS): Allow tissue sampling (cytology, biopsy, brushings) for histopathological analysis, particularly useful for cystic lesions (e.g., pancreas).
  • Tumor Seeding: A significant risk, especially with core biopsies and certain tumor types (e.g., soft tissue sarcomas). Needle track placement should be planned with the surgeon to allow excision during definitive surgery. Ablation of the biopsy track may reduce risk.
  • Transcoelomic Biopsies: Generally avoided unless discussed in an MDT (Multidisciplinary Team) appropriate to the suspected tumor type, and only when radiological diagnosis is insufficient and surgical resection isn't a curative option (e.g., colorectal liver metastases).
II. Biopsy Procedures and Considerations:
  • Cytology Sample Examination: Requires experienced cytopathologists.
  • Incisional Biopsy: Should not compromise future definitive surgery.
  • Excisional Biopsy: Ideally performed by the surgeon undertaking definitive surgery, particularly crucial for melanoma (2mm margin recommended for suspicious lesions). Margin controversy exists depending on melanoma depth.
  • Specialized Staining/Analysis: Close surgeon-pathologist collaboration is vital when specialized staining (e.g., immunohistochemistry), electron microscopy, or cytogenetic analyses are needed (e.g., lymph node excision for lymphoma – tissue should be sent fresh).
III. Laparoscopy in Diagnosis and Staging:
  • Laparoscopic Biopsy: Valuable for accessing areas difficult for image-directed biopsy (e.g., mesentery, retroperitoneal space).
  • Peritoneal Washing Cytology: Used in staging upper abdominal malignancies. 500mL of warm saline is instilled, agitated, and aspirated for cytological analysis. Detection of tumor cells indicates poor prognosis.
  • Intraoperative Ultrasonography: Allows detection and biopsy (even treatment via laparoscopic ablation) of lesions, including those <1cm, in solid organs (e.g., liver). doppler ultrasound aids avoiding vascular structures.< />pan>
IV. Key Points to Remember:
  • The choice of biopsy technique depends on the suspected diagnosis, tumor type, and access to resources.
  • Minimizing the risk of tumor seeding is crucial, requiring careful planning and potentially preventative measures.
  • Multidisciplinary collaboration between radiologists, pathologists, surgeons, and other specialists is essential for optimal diagnosis and staging.
  • Advanced imaging techniques guide biopsy procedures, increasing accuracy.
  • Laparoscopy offers valuable diagnostic and staging capabilities, particularly for challenging locations.​
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Oncology-Curative Surgery
This study guide summarizes the provided text on curative cancer surgery, focusing on key concepts for improved understanding and retention.
I. Factors Influencing Long-Term Outcomes:
  • Tumor Type and Stage: The most significant determinants of long-term survival after cancer surgery. Earlier detection (due to screening and awareness) improves outcomes for cancers like breast and cervical cancer.
  • Surgical and Anesthetic Advances: Allow for more extensive resections with reduced morbidity and mortality, improving functional outcomes (e.g., limb-preserving surgery). However, limitations remain, especially in CNS tumors due to vital structures.
  • 5-Year Survival Rates: Vary drastically across cancer types. High survival rates are seen in breast cancer (>80%) and large bowel cancer (~70% in the US). However, pancreatic, gastric, and lung cancers have significantly lower 5-year survival rates (<10%, <10%, and 15%, respectively).< />pan>
  • Microscopically Negative Margins: Achieving clear margins (absence of cancerous cells at the resection site) is crucial for long-term survival. This necessitates close collaboration between surgeons and pathologists.
II. Margin Requirements and Controversies:
  • Breast Cancer: Wide local excision requires 0.5-1cm clear margins, often followed by radiotherapy. However, some surgeons accept smaller margins (a few mm), leading to ongoing debate.
  • Colorectal Cancer: Requires a 5cm proximal and 2cm distal margin for adequate clearance. Maintaining these margins is particularly important during the learning curve of laparoscopic procedures.
  • Rectal Cancer: Total mesorectal excision is essential to prevent pelvic recurrence. Specialization in rectal cancer surgery significantly improves outcomes.
  • Multifocal Cancers (e.g., Papillary Thyroid Cancer): May necessitate wider resections (e.g., total thyroidectomy) to remove all tumor foci. Controversy exists, with total lobectomy sometimes sufficient.
  • High-Volume Centers and Specialists: Growing evidence suggests that major oncological surgeries should be performed by specialists in high-volume centers (e.g., rectal, esophageal, gastric, and pancreatic cancers) to optimize outcomes.
III. Laparoscopic Techniques:
  • Early Advantages: Laparoscopic surgery showed promise in reducing postoperative morbidity and accelerating recovery.
  • Oncological Adequacy Concerns: Initial concerns regarding achieving adequate oncological clearance were addressed by long-term follow-up studies.
  • Current Evidence: Long-term studies in colorectal, renal, prostatic, and gynecological cancers demonstrate comparable negative margin rates, lymph node yields, and disease-free survival (DFS) to open surgery. Data for gastric, esophageal, pancreatic, and hepatic malignancies are still emerging.
Key Terms:
  • Morbidity: Illness or impairment resulting from disease or treatment.
  • Mortality: Death rate.
  • Resection: Surgical removal of a part of an organ or structure.
  • Margins: The tissue surrounding a tumor that is removed during surgery.
  • Disease-Free Survival (DFS): The length of time after treatment that a person lives without any signs or symptoms of the disease.
  • Overall Survival (OS): The length of time after diagnosis that a person lives.
  • CNS: Central nervous system.
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Oncology- Electron Beam Therapy
I. Electron Beam Therapy vs. Photon Radiotherapy
A. Fundamental Difference: Electron beams, unlike photons, possess charge. This leads to frequent interactions within tissue, resulting in a defined range of penetration and negligible dose beyond that range. Photons penetrate deeper.
B. Electron Beam Advantages:
  • Limited penetration: Ideal for superficial tumors, minimizing damage to underlying structures.
  • Negligible exit dose: Reduces radiation exposure to tissues beyond the target.
  • Superficial tumor treatment: Particularly useful for skin cancer, head and neck cancers, and breast cancer.
  • Reduced normal tissue dose: Minimizes damage to critical structures like the spinal cord and lungs.
C. Photon Beam Advantages:
  • Deep penetration: Suitable for deep-seated cancers.
  • Skin sparing: Delivers less radiation to the skin surface.
  • Easier beam matching: Facilitates precise treatment planning with crossfire techniques.
II. Production of Electron Beams
  • Linear Accelerators: Most radiotherapy facilities use linear accelerators to produce both X-ray and electron beams.
  • Beam Collimation: Due to significant air scattering, collimators (cones or trimmer bars) are used to shape the beam near the skin's surface. Further shaping can be achieved with lead apertures or lead sheets placed directly on the skin.
III. Dosimetric Characteristics of Electron Beams
A. Depth Dose Characteristics:
  • Dose buildup: The dose increases gradually to a maximum and then drops sharply to near zero at the practical range.
  • Practical Range (Rp): The depth at which the dose becomes negligible. Approximated by Rp ≈ E0 / 2. (E0 = incident beam energy in MeV)
  • Clinically Useful Range (d80): The depth where the dose falls to 80% of its maximum. Approximated by d80 ≈ E0 / 3.
  • Surface Dose: Significantly higher for electron beams than photon beams (85-95% of maximum dose, depending on energy).
B. Effect of Incident Energy: Higher incident energy (E0) leads to greater penetration depth. Common energies range from 6-15 MeV.
C. Beam Profile and Penumbra:
  • Larger Penumbra: Electron beams have a larger penumbra (area of dose falloff) than photon beams. A 10x10 cm² beam might only deliver a clinically useful dose to an 8x8 cm² area.
  • Abutment Challenges: The large penumbra makes combining electron and photon beams difficult, hindering uniform dose delivery across field junctions.
IV. Key Concepts to Remember
  • Charge and Interaction: Electrons' charge leads to their limited penetration and well-defined range.
  • Superficial vs. Deep: Electron beams are for superficial tumors, photons for deep-seated ones.
  • Penumbra: Electron beams have a larger penumbra than photon beams, affecting treatment planning.
  • Range Calculation: Understand the approximations for practical and clinically useful range based on incident energy.
  • Surface Dose: Electron beams have a higher surface dose than photon beams.



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Oncology-External Beam Radiotherapy: Progress & Techniques
This study guide summarizes advancements in external beam radiotherapy, focusing on 3D planning and conformal treatment.
I. Three-Dimensional (3D) Radiotherapy Planning:
  • Revolutionizing Factor: The most significant advancement in the last 20 years is the integration of cross-sectional imaging (primarily CT scans) into radiotherapy planning. This shift enables:
    • Accurate Target Definition: Precise delineation of tumors and critical structures.
    • Precise Dose Calculation: More accurate determination of radiation dosage.
    • True 3D Planning: Allows for:
      • Reduced Normal Tissue Damage: Minimizing harm to healthy tissue.
      • Increased Tumor Dose: Delivering higher radiation doses to the cancerous target.
      • Improved Therapeutic Index: Optimizing the balance between tumor control and side effects.
Key takeaway: 3D planning using CT scans significantly improves accuracy and allows for better treatment optimization, leading to improved outcomes.
II. Conformal Treatment and Multileaf Collimators (MLCs):
  • Goal: The primary goal of radiotherapy has always been to precisely conform the high-dose radiation to the target tumor while sparing surrounding healthy tissue.
  • Traditional Limitations: Until the 1990s, rectangular beams with limited blocking techniques resulted in unnecessary irradiation of normal tissue.
  • Advancements:
    • Shaped Alloy Blocks: Improved conformation by manually placing shaped blocks to partially obstruct the radiation beam.
    • Multileaf Collimators (MLCs): A significant advancement integrated into modern linear accelerators. MLCs allow for computer-controlled shaping of the radiation beam using numerous 0.5cm-wide leaves. This enables highly precise shaping of the radiation field.
  • Clinical Significance: By minimizing high-dose radiation to normal tissue, MLCs enable higher radiation doses to the tumor, potentially improving tumor control without increasing the risk of side effects (morbidity).
Key takeaway: MLCs are a crucial technology for conformal radiotherapy. They allow for precise shaping of the radiation beam, maximizing tumor dose while minimizing damage to healthy tissues. This improves the therapeutic ratio, aiming for better tumor control with fewer side effects.


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Oncology-Recent Advances in External Beam Radiotherapy (EBRT)
I. Improved Accuracy and Precision
A. Volume Definition:
  • Past: Planning scans relied on diagnostic scanners, resulting in less precise tumor volume definition.
  • Present: High-resolution CT simulators are standard. 3D tumor volume definition is now accurate even for palliative treatments. Fusion of CT with MRI and PET scans further refines this for radical treatments.
B. Image-Guided Radiotherapy (IGRT):
  • Past: A 1cm margin was added to the Clinical Target Volume (CTV) to account for positioning errors. Megavoltage X-rays provided low-quality confirmation images.
  • Present:
    • Electronic Portal Imaging Devices (EPIDs): Replaced port films, offering improved image quality. Online imaging corrects misalignments before treatment, while offline review identifies recurring setup errors.
    • Intra-treatment Imaging: Precise tumor location is confirmed during treatment using:
      • Fiducial markers (e.g., gold seeds)
      • Ultrasound
      • Cone beam CT (mounted on the linear accelerator) for 3D online imaging.
II. Minimizing Radiation Exposure to Organs at Risk & Higher Tumor Doses
A. Inverse Planned Intensity-Modulated Radiotherapy (IMRT):
  • Mechanism: Computer optimization varies radiation beam intensity to meet dose constraints for healthy organs while delivering prescribed doses to the tumor (CTV and Gross Tumor Volume - GTV). This is achieved through:
    • Step and shoot: Superimposing static uniform intensity segments.
    • Dynamic MLC delivery: A shaped sliding window across the field.
    • Tomotherapy: Multiple arcs with intensity modulated by dynamic MLCs.
  • Benefits: Reduced late effects on normal tissues with equivalent cancer control compared to conventional radiotherapy, particularly in prostate and head/neck cancers. Promising results in lung and gynecological cancers suggest it may replace 3D conformal radiotherapy (CRT) for many radical treatments.
  • Drawback: Significantly increases the workload of the physics team due to the extensive time (at least 2 hours per patient) required for meticulous volume definition.
B. Four-Dimensional (4D) Therapy Planning and Delivery:
  • Addresses the challenge of: Treating mobile structures (e.g., lung cancers moving with respiration).
  • Method: Links 4D CT planning (tumor volume defined at each respiratory phase) to treatment delivery during the expiratory phase for optimal coverage with minimal field size.
C. Stereotactic Radiotherapy:
  • Established for: Intracranial conditions (benign tumors, arteriovenous malformations).
  • Method: High precision (1-2mm) treatment of small lesions (<1cm3) using an external 3d coordinate system and stereotactic fixation. typically uses 1-3 large fractions (12-20 gy).< />pan>
  • Recent expansion: Successful treatment of small malignancies in the brain, lung, and liver. IGRT facilitates accuracy in sites unsuitable for localization frames.
III. Key Terms & Concepts to Remember:
  • CTV: Clinical Target Volume
  • GTV: Gross Tumor Volume
  • EPID: Electronic Portal Imaging Device
  • IMRT: Intensity-Modulated Radiotherapy
  • MLC: Multileaf Collimator
  • IGRT: Image-Guided Radiotherapy
  • 4D: Four-Dimensional (referring to respiratory gating)
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Kembara Xtra 

Facts about medicine and its subtopic such as anatomy, physiology, biochemistry, pharmacology, medicine, pediatrics, psychiatry, obstetrics and gynecology and surgery.