Targeted Therapy Concepts — MCQs
Fluorescence in situ hybridization (FISH) is required in which of the following interpretations of Her2/neu?
Ranibizumab is a monoclonal antibody against?
What is the treatment for Dabigatran toxicity?
Osimertinib is used in NSCLC with which mutation?
Which of the following is a monoclonal antibody used in cancer treatment?
What is the mechanism of action of Bevacizumab?
What is the most appropriate next step in management for a patient with a Stage III ovarian cancer with partial response to platinum-based chemotherapy?
Production of inactivating enzymes is an important mechanism of drug resistance for all of these antibiotics EXCEPT
Bragg peak effect is most pronounced in:
What is the definition of a sentinel lymph node?
Targeted Therapy Concepts Indian Medical PG Practice Questions and MCQs
Question 1: Fluorescence in situ hybridization (FISH) is required in which of the following interpretations of Her2/neu?
- A. All of the options
- B. 2+ (Correct Answer)
- C. 1+
- D. 3+
Explanation: ***Correct: 2+*** A **Her2/neu immunohistochemistry (IHC) score of 2+** is considered **equivocal**, meaning it's uncertain whether Her2/neu is overexpressed. In such cases, **Fluorescence In Situ Hybridization (FISH)** is required to determine the amplification status of the *HER2* gene, which guides treatment decisions regarding anti-HER2 therapy (trastuzumab) [1], [2]. The 2+ score shows incomplete and weak to moderate membrane staining in >10% of tumor cells, necessitating gene amplification confirmation. *Incorrect: All of the options* While FISH is crucial for equivocal interpretations, it is **not required for all** possible Her2/neu IHC results [2]. Some scores (1+ and 3+) definitively indicate Her2/neu status without requiring confirmatory testing. Routinely performing FISH for all IHC scores would be unnecessary and costly. *Incorrect: 1+* An IHC score of **1+** indicates **no Her2/neu overexpression** (faint/barely perceptible incomplete membrane staining in >10% of tumor cells). In this situation, the patient is considered **Her2-negative**, and FISH testing is **not required** as the result is clearly negative. *Incorrect: 3+* An IHC score of **3+** indicates **clear Her2/neu overexpression** (strong, complete membrane staining in >10% of tumor cells) [1]. Patients with an IHC 3+ score are considered **Her2-positive**, and typically **FISH testing is not required** to confirm this result, as the overexpression is unequivocal [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 256-259. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, pp. 1064-1066.
Question 2: Ranibizumab is a monoclonal antibody against?
- A. VEGF (Correct Answer)
- B. Interleukin-6
- C. Cluster of Differentiation 20
- D. Epidermal Growth Factor Receptor
Explanation: ***VEGF*** - **Ranibizumab** is a **monoclonal antibody** specifically designed to inhibit **vascular endothelial growth factor A (VEGF-A)**. - By binding to VEGF-A, ranibizumab prevents its interaction with receptors on endothelial cells, thereby inhibiting **angiogenesis** and reducing vascular permeability, which is crucial in treating conditions like **wet age-related macular degeneration (AMD)** and **diabetic macular edema**. *Interleukin-6* - **Interleukin-6 (IL-6)** is a **pro-inflammatory cytokine** involved in various autoimmune and inflammatory diseases. - Monoclonal antibodies targeting IL-6, such as **tocilizumab**, are used in conditions like **rheumatoid arthritis** and **cytokine release syndrome**, not for ocular neovascularization. *Cluster of Differentiation 20* - **Cluster of Differentiation 20 (CD20)** is a protein found on the surface of **B lymphocytes**. - Monoclonal antibodies against CD20, like **rituximab**, are used in the treatment of **B-cell lymphomas**, **leukemia**, and certain **autoimmune diseases**, not for conditions requiring anti-VEGF therapy. *Epidermal Growth Factor Receptor* - The **epidermal growth factor receptor (EGFR)** is a **tyrosine kinase receptor** involved in cell growth and proliferation. - Monoclonal antibodies targeting EGFR, such as **cetuximab** and **panitumumab**, are used in the treatment of various **cancers**, particularly **colorectal cancer** and **head and neck cancer**.
Question 3: What is the treatment for Dabigatran toxicity?
- A. Protamine sulphate
- B. Andexanet alfa
- C. Idarucizumab (Correct Answer)
- D. Argatroban
Explanation: ***Idarucizumab*** - **Idarucizumab** is a specific humanized monoclonal antibody fragment (Fab) that directly binds to dabigatran and its metabolites, effectively **reversing its anticoagulant effects**. - It is indicated for patients requiring urgent reversal of dabigatran's anticoagulant effects due to life-threatening or uncontrolled bleeding, or for emergency surgery/urgent procedures. *Protamine sulphate* - **Protamine sulphate** is used to reverse the anticoagulant effects of **heparin** and low molecular weight heparins, but it is ineffective against direct oral anticoagulants like dabigatran. - Its mechanism involves forming a stable ion pair with heparin, neutralizing its activity. *Andexanet alfa* - **Andexanet alfa** is a recombinant modified human factor Xa (FXa) decoy protein used to reverse the anticoagulant activity of **FXa inhibitors** (e.g., rivaroxaban, apixaban). - It does not bind to or reverse the effects of direct thrombin inhibitors like dabigatran. *Argatroban* - **Argatroban** is a **direct thrombin inhibitor** (similar mechanism of action to dabigatran) and is used as an anticoagulant, particularly in patients with heparin-induced thrombocytopenia. - It would worsen dabigatran toxicity rather than treat it, as both drugs inhibit thrombin.
Question 4: Osimertinib is used in NSCLC with which mutation?
- A. L858R mutation
- B. M790T mutation
- C. T890M mutation
- D. T790M mutation (Correct Answer)
Explanation: ***T790M mutation*** - **Osimertinib** is a third-generation **EGFR tyrosine kinase inhibitor (TKI)** specifically designed to overcome resistance to earlier generation EGFR TKIs. - The **T790M mutation** in the EGFR gene is the most common mechanism of acquired resistance to first and second-generation EGFR TKIs in non-small cell lung cancer (NSCLC). *L858R mutation* - The **L858R mutation** is an activating **EGFR mutation** typically sensitive to first and second-generation EGFR TKIs. - While patients with **L858R** may eventually develop resistance, **osimertinib** is primarily used in the setting of acquired resistance, often mediated by **T790M**. *M790T mutation* - This is not a recognized common or clinically significant activating or resistance mutation in the **EGFR gene** for NSCLC. - The correct resistance mutation that **osimertinib** targets is **T790M**, not **M790T**. *T890M mutation* - This is a typographical error for the clinically relevant **T790M mutation**. - The number sequence is critical for identifying specific amino acid substitutions in gene mutations.
Question 5: Which of the following is a monoclonal antibody used in cancer treatment?
- A. Cisplatin
- B. Rituximab (Correct Answer)
- C. 5-fluorouracil
- D. Methotrexate
Explanation: ***Rituximab*** - **Rituximab** is a **chimeric monoclonal antibody** that targets the **CD20 protein** found on the surface of normal and malignant **B lymphocytes**. - It is widely used in the treatment of various **lymphomas** and **leukemias**, as well as autoimmune diseases, by inducing the death of CD20-positive B cells. *Cisplatin* - **Cisplatin** is a **platinum-based chemotherapy drug** that works by forming **DNA adducts**, leading to DNA damage and apoptosis of cancer cells. - It is used in various solid tumors but is not a monoclonal antibody; it's a **cytotoxic agent**. *5-fluorouracil* - **5-fluorouracil (5-FU)** is an **antimetabolite chemotherapy drug** that interferes with DNA and RNA synthesis, thereby inhibiting cell division. - It is a **pyrimidine analog** and not a monoclonal antibody. *Methotrexate* - **Methotrexate** is a **folate analog antimetabolite** that inhibits **dihydrofolate reductase**, interfering with DNA synthesis and cell proliferation. - It's a conventional chemotherapy agent and immunosuppressant, not a monoclonal antibody.
Question 6: What is the mechanism of action of Bevacizumab?
- A. Anti VEGF antibody (Correct Answer)
- B. Histone deacetylase inhibitor
- C. HER2 neu inhibitor
- D. Proteasome inhibitor
Explanation: ***Anti VEGF antibody*** - **Bevacizumab** is a **monoclonal antibody** that specifically targets and binds to vascular endothelial growth factor (VEGF). - By inhibiting VEGF, bevacizumab prevents the formation of new blood vessels (**angiogenesis**) that tumors need to grow and metastasize. *Histone deacetylase inhibitor* - **Histone deacetylase (HDAC) inhibitors** influence gene expression by modifying chromatin structure, leading to cell cycle arrest and apoptosis in cancer cells. - They are used in certain hematologic malignancies and solid tumors but do not directly interfere with angiogenesis. *Proteasome inhibitor* - **Proteasome inhibitors** like bortezomib block the action of proteasomes, leading to an accumulation of ubiquitinated proteins and induction of apoptosis in cancer cells. - This mechanism is distinct from blocking new blood vessel formation. *HER2 neu inhibitor* - **HER2 neu inhibitors** (e.g., trastuzumab) specifically target the HER2/neu receptor, which is overexpressed in certain breast and gastric cancers. - Their action primarily involves blocking growth signals transmitted through this receptor, not inhibiting VEGF or angiogenesis.
Question 7: What is the most appropriate next step in management for a patient with a Stage III ovarian cancer with partial response to platinum-based chemotherapy?
- A. Bevacizumab
- B. Perform surgery (Correct Answer)
- C. Switch to radiotherapy
- D. Continue regimen
Explanation: ***Perform surgery (Interval Debulking Surgery)*** - In **Stage III ovarian cancer**, after an initial partial response to **platinum-based chemotherapy**, **interval debulking surgery** is the standard next step to remove residual disease. - This approach aims to reduce tumor burden to an optimal level (< 1 cm residual disease), which has been shown to improve overall survival in multiple trials (EORTC 55971, GOG-152). - Performed after 3-4 cycles of neoadjuvant chemotherapy when the patient has demonstrated response and is medically fit for surgery. *Bevacizumab* - **Bevacizumab** is an **anti-angiogenic agent** used in ovarian cancer, typically as part of frontline maintenance therapy or for recurrent disease, not as the immediate next step after partial response to primary chemotherapy when surgery is feasible. - While it can be incorporated into maintenance treatment post-surgery, it's not the primary next step after partial response when interval debulking surgery is indicated. *Switch to radiotherapy* - **Radiotherapy** has a limited role in the primary treatment of advanced ovarian cancer due to its widespread peritoneal nature. - It is sometimes used for localized recurrence or symptom palliation, but not as a standard next step after partial response to chemotherapy in Stage III disease. *Continue regimen* - Continuing the same regimen after only a **partial response** is generally not the most effective strategy when further tumor reduction via surgery is possible. - The goal in advanced ovarian cancer is **maximal cytoreduction**, and if residual disease is present after neoadjuvant chemotherapy, interval debulking surgery is preferred over continued chemotherapy alone.
Question 8: Production of inactivating enzymes is an important mechanism of drug resistance for all of these antibiotics EXCEPT
- A. Quinolone (Correct Answer)
- B. Penicillin
- C. Chloramphenicol
- D. Aminoglycoside
Explanation: ***Quinolone*** - The primary mechanisms of resistance to **quinolones** involve mutations in the **gyrase** and **topoisomerase IV** enzymes or efflux pump overexpression, rather than enzymatic inactivation of the drug itself. - Unlike other antibiotic classes listed, quinolones are not typically susceptible to bacterial enzymes that degrade or modify their structure. *Penicillin* - **Penicillins** are highly susceptible to inactivation by **beta-lactamase enzymes**, which hydrolyze the beta-lactam ring, rendering the antibiotic ineffective. - This enzymatic degradation is a major mechanism of resistance developed by many bacterial species to penicillin and other beta-lactam antibiotics. *Chloramphenicol* - Resistance to **chloramphenicol** is primarily mediated by the enzyme **chloramphenicol acetyltransferase (CAT)**, which acetylates the drug, preventing its binding to the bacterial ribosome. - This enzymatic modification is a classic example of drug inactivation leading to resistance. *Aminoglycoside* - **Aminoglycosides** are frequently inactivated by a variety of **aminoglycoside-modifying enzymes (AMEs)**, such as acetyltransferases, phosphoryltransferases, and nucleotidyltransferases. - These enzymes add chemical moieties to the aminoglycoside molecule, preventing its binding to the bacterial ribosome and inhibiting protein synthesis.
Question 9: Bragg peak effect is most pronounced in:
- A. Neutron
- B. Electron
- C. Proton (Correct Answer)
- D. X ray
Explanation: ***Proton*** - The **Bragg peak** is a sharp increase in the dose deposition of a particle beam, like protons, just before it stops, allowing precise energy delivery to tumors while sparing surrounding healthy tissue. - This effect is most pronounced in **heavy charged particles** like protons and alpha particles, which deposit most of their energy at the end of their range. *Neutron* - **Neutrons** are uncharged particles; they do not exhibit a Bragg peak because their primary mode of energy deposition is through nuclear interactions and scattering, not direct ionization along a well-defined path. - While used in neutron capture therapy, the dose distribution is fundamentally different from that of charged particles as they deposit energy more uniformly along their path. *Electron* - **Electrons** are light charged particles and do not exhibit a pronounced Bragg peak due to their small mass and higher scattering, which causes a more gradual energy deposition as they traverse tissue. - Electron beams have a relatively shallow penetration and a more spread-out dose distribution, making them suitable for superficial tumors but not for deep-seated precise energy deposition like protons. *X ray* - **X-rays** (photons) deposit energy in a continuously decreasing manner as they pass through tissue, meaning they do not exhibit a Bragg peak. - Their dose distribution is characterized by an initial build-up region followed by an exponential decay, making precise dose localization more challenging compared to proton therapy.
Question 10: What is the definition of a sentinel lymph node?
- A. The primary lymph node draining the tumor. (Correct Answer)
- B. The first lymph node excised during a modified radical mastectomy.
- C. The lymph node located nearest to the tumor.
- D. None of the above.
Explanation: ### Explanation **Concept Overview** The **Sentinel Lymph Node (SLN)** is defined as the first lymph node (or group of nodes) in a regional lymphatic basin that receives direct lymphatic drainage from a primary tumor. The underlying physiological principle is that lymphatic metastasis occurs in an orderly, step-wise fashion. If the sentinel node is negative for malignancy, there is a high probability (usually >95%) that the remaining nodes in that basin are also free of disease. **Analysis of Options** * **Option A (Correct):** This aligns with the physiological definition. It is the "gatekeeper" node. If the tumor spreads via lymphatics, this node is the first site of metastasis. * **Option B (Incorrect):** A Modified Radical Mastectomy (MRM) involves a formal axillary lymph node dissection (Levels I and II). The nodes removed are based on anatomical boundaries, not necessarily the specific drainage pattern of the tumor. * **Option C (Incorrect):** Proximity does not always equal drainage. Due to the complexity of lymphatic channels, the sentinel node may sometimes be anatomically distant from the tumor while still being the first node to receive its drainage. **Clinical Pearls for NEET-PG** * **Identification:** SLN is identified using **Isosulfan blue/Methylene blue dye** (visualized) and/or **Technetium-99m labeled sulfur colloid** (detected via a gamma probe). * **Most Common Indications:** Breast cancer (T1/T2 lesions) and Malignant Melanoma. * **Skip Metastasis:** This refers to a phenomenon where the SLN is negative, but higher-level nodes are positive. While rare, it is a limitation of SLN biopsy. * **Contraindications in Breast Cancer:** Inflammatory breast cancer, multicentric tumors (relative), and clinically palpable axillary nodes (N1/N2).
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