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Egyptian Board Clinical Oncology study materials
Egyptian Board Clinical Oncology study resources

Egyptian Board Clinical Oncology practice questions

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Question 1Medical Oncology: Systemic Therapy and Drug Classes

A patient with metastatic colorectal cancer is being considered for an anti-EGFR monoclonal antibody. Which molecular result is required before such therapy is appropriate?

  1. RAS wild-type status in the tumour Correct answer.
  2. BRAF V600E mutation positivity
  3. HER2 gene amplification
  4. MSI-high status

Explanation

Anti-EGFR antibodies such as cetuximab and panitumumab benefit only patients whose tumours lack activating RAS mutations, because constitutive RAS signalling bypasses EGFR blockade. Guidelines therefore mandate RAS (KRAS and NRAS) testing before use. Other biomarkers predict response to different agents, not to anti-EGFR antibodies.

Question 2Medical Oncology: Systemic Therapy and Drug Classes

Which cytotoxic mechanism best describes the action of oxaliplatin?

  1. Formation of platinum-DNA adducts that crosslink and block replication Correct answer.
  2. Irreversible inhibition of thymidylate synthase
  3. Inhibition of topoisomerase I by stabilising the enzyme-DNA cleavage complex
  4. Depolymerisation of microtubules preventing mitotic spindle formation

Explanation

Oxaliplatin is a third-generation platinum compound whose reactive species bind DNA to form intra- and interstrand crosslinks, arresting replication and transcription. This is the shared class mechanism of platinum agents. The other options describe camptothecins, vinca alkaloids, and fluoropyrimidines respectively.

Question 3Medical Oncology: Systemic Therapy and Drug Classes

A woman receiving adjuvant tamoxifen for hormone receptor-positive breast cancer asks about a recognised serious adverse effect. Which risk should be discussed?

  1. Pulmonary fibrosis
  2. Haemorrhagic cystitis
  3. Endometrial carcinoma Correct answer.
  4. Peripheral neuropathy

Explanation

Tamoxifen acts as a selective oestrogen receptor modulator with partial agonist activity in the endometrium, increasing the risk of endometrial hyperplasia and carcinoma. This is a well-established serious toxicity requiring counselling about abnormal vaginal bleeding. The other listed toxicities belong to different drug classes.

Question 4Medical Oncology: Systemic Therapy and Drug Classes

Which agent is a humanised monoclonal antibody that binds the HER2 extracellular domain and is standard in HER2-positive early breast cancer?

  1. Trastuzumab Correct answer.
  2. Anastrozole
  3. Everolimus
  4. Lapatinib

Explanation

Trastuzumab is a humanised IgG1 monoclonal antibody directed against the extracellular domain of HER2, producing antibody-dependent cellular cytotoxicity and downstream signalling blockade. It is a cornerstone of HER2-positive breast cancer therapy in both early and advanced settings. The alternatives act through different mechanisms.

Question 5Medical Oncology: Systemic Therapy and Drug Classes

A patient on high-dose methotrexate develops mucositis and cytopenias with rising creatinine. Which intervention is the specific antidote for methotrexate toxicity?

  1. Palifermin
  2. Dexrazoxane
  3. Leucovorin (folinic acid) Correct answer.
  4. Mesna

Explanation

Leucovorin is a reduced folate that bypasses the dihydrofolate reductase blockade caused by methotrexate, rescuing normal tissues. It is given as rescue after high-dose therapy and therapeutically in overdose. The other agents antidote different toxicities.

Question 6Medical Oncology: Systemic Therapy and Drug Classes

Which class of agents directly inhibits the proteasome and is used in multiple myeloma?

  1. Bortezomib Correct answer.
  2. Imatinib
  3. Rituximab
  4. Letrozole

Explanation

Bortezomib is a reversible proteasome inhibitor that blocks degradation of ubiquitinated proteins, causing endoplasmic reticulum stress and apoptosis in myeloma cells. It is a backbone agent in multiple myeloma regimens. The other options target different pathways.

Question 7Medical Oncology: Systemic Therapy and Drug Classes

Which toxicity is most characteristic of bleomycin-containing regimens and requires cumulative dose monitoring?

  1. Nephrotoxicity
  2. Pulmonary fibrosis Correct answer.
  3. Cardiomyopathy
  4. Ototoxicity

Explanation

Bleomycin causes dose-dependent pneumonitis progressing to pulmonary fibrosis, so cumulative dose limits and periodic assessment of respiratory symptoms are standard. Cardiomyopathy, nephrotoxicity, and ototoxicity are not the signature toxicity of bleomycin.

Question 8Medical Oncology: Systemic Therapy and Drug Classes

A patient with non-small cell lung cancer is started on pembrolizumab. Which mechanism describes this drug's action?

  1. Blockade of PD-1 receptors on T cells, restoring antitumour immunity Correct answer.
  2. Inhibition of CTLA-4, enhancing T-cell priming in lymph nodes
  3. Direct lysis of tumour cells by complement activation
  4. Depletion of regulatory T cells by anti-CD25 antibody

Explanation

Pembrolizumab is a humanised IgG4 antibody that binds PD-1 on T lymphocytes, preventing interaction with PD-L1 and PD-L2 and thereby releasing T-cell effector activity. This distinguishes it from CTLA-4 inhibitors. The other mechanisms do not describe pembrolizumab.

Question 9Medical Oncology: Systemic Therapy and Drug Classes

A 60-year-old man with metastatic renal cell carcinoma is prescribed sunitinib. Which monitoring parameter is most important during therapy?

  1. Serum TSH only
  2. Pulmonary function tests
  3. Blood pressure Correct answer.
  4. Visual acuity

Explanation

Sunitinib is a multitargeted tyrosine kinase inhibitor that inhibits VEGF receptors and commonly causes hypertension, sometimes severe. Blood pressure must be measured regularly and treated. Thyroid function and other parameters may be checked but are not the primary safety focus compared with blood pressure.

Question 10Medical Oncology: Systemic Therapy and Drug Classes

A patient with hormone receptor-positive, HER2-negative metastatic breast cancer has progressed on an aromatase inhibitor. Which class of agent combined with endocrine therapy improves outcomes by targeting CDK4/6?

  1. Fulvestrant
  2. Olaparib
  3. Capecitabine
  4. Palbociclib Correct answer.

Explanation

Palbociclib is a CDK4/6 inhibitor that arrests cells in G1 by preventing phosphorylation of retinoblastoma protein; combined with endocrine therapy it improves progression-free survival. Olaparib is a PARP inhibitor, capecitabine a fluoropyrimidine, and fulvestrant an oestrogen receptor degrader without CDK4/6 activity.

Question 11Medical Oncology: Systemic Therapy and Drug Classes

A patient with chronic myeloid leukaemia in chronic phase is started on imatinib. Which molecular target mediates its therapeutic effect?

  1. BCR-ABL tyrosine kinase Correct answer.
  2. JAK2
  3. BRAF
  4. ALK

Explanation

Imatinib inhibits the BCR-ABL fusion tyrosine kinase that characterises chronic myeloid leukaemia, inducing durable haematological and cytogenetic remissions. JAK2, BRAF, and ALK are targets of other agents used in different diseases.

Question 12Medical Oncology: Systemic Therapy and Drug Classes

A woman receiving paclitaxel develops acute severe hypersensitivity during infusion. Which premedication strategy is standard to reduce this risk before subsequent taxane infusions?

  1. Oral leucovorin
  2. Prophylactic antibiotics
  3. Granulocyte colony-stimulating factor
  4. Corticosteroid, antihistamine, and H2 blocker Correct answer.

Explanation

Paclitaxel hypersensitivity is largely related to the Cremophor vehicle and is mitigated by premedication with a corticosteroid, an antihistamine, and an H2 receptor antagonist. G-CSF, leucovorin, and antibiotics address different problems.

Question 13Medical Oncology: Systemic Therapy and Drug Classes

A patient with advanced pancreatic cancer is started on gemcitabine. Which toxicity pattern is most typical?

  1. Irreversible cardiomyopathy
  2. Myelosuppression, particularly thrombocytopenia, with a flu-like syndrome Correct answer.
  3. Haemorrhagic cystitis
  4. Severe mucositis only

Explanation

Gemcitabine is a nucleoside analogue that commonly causes myelosuppression, especially thrombocytopenia, and a flu-like syndrome. Mucositis can occur but is not the dominant pattern, and the other toxicities are not characteristic.

Question 14Medical Oncology: Systemic Therapy and Drug Classes

A patient with metastatic melanoma harbouring a BRAF V600E mutation is started on vemurafenib. Which dermatological adverse effect is most characteristic and requires surveillance?

  1. Cutaneous squamous cell carcinoma and keratoacanthoma Correct answer.
  2. Acral hyperpigmentation
  3. Erythroderma
  4. Diffuse alopecia

Explanation

Paradoxical activation of the MAPK pathway in BRAF wild-type keratinocytes leads to squamous cell carcinomas and keratoacanthomas in patients on BRAF inhibitors. Regular skin examination and prompt excision are required. The other options are not the hallmark dermatological toxicity.

Question 15Medical Oncology: Systemic Therapy and Drug Classes

A patient with ovarian cancer is treated with carboplatin and develops a delayed hypersensitivity reaction after several cycles. Which approach is standard for managing this reaction while continuing platinum therapy?

  1. Permanent discontinuation of all platinum agents
  2. Desensitisation protocol with premedication Correct answer.
  3. Switch to single-agent doxorubicin
  4. Addition of G-CSF only

Explanation

Carboplatin hypersensitivity often appears after multiple cycles; a graded desensitisation protocol with antihistamines and corticosteroids allows continued treatment when platinum is essential. Permanent discontinuation is reserved for severe refractory reactions. The other options do not address the hypersensitivity.

Question 16Medical Oncology: Systemic Therapy and Drug Classes

Which statement best describes the mechanism of capecitabine?

  1. A direct inhibitor of topoisomerase II
  2. A monoclonal antibody against VEGF
  3. An oral fluoropyrimidine prodrug converted to 5-fluorouracil preferentially within tumour tissue Correct answer.
  4. An alkylating agent that crosslinks DNA

Explanation

Capecitabine undergoes sequential enzymatic conversion to 5-fluorouracil, with the final step mediated by thymidine phosphorylase, which is more abundant in tumour tissue. This provides relative tumour selectivity. It does not inhibit topoisomerase II, alkylate DNA, or target VEGF.

Question 17Medical Oncology: Systemic Therapy and Drug Classes

A patient on cisplatin develops a rise in creatinine after the first cycle. Which preventive measure best reduces cisplatin nephrotoxicity?

  1. Routine furosemide before each dose
  2. Vigorous intravenous hydration with normal saline Correct answer.
  3. Oral potassium supplementation alone
  4. Prophylactic erythropoietin

Explanation

Cisplatin nephrotoxicity results from tubular injury, and vigorous saline hydration with attention to urine output is the mainstay of prevention. Mannitol or diuretics are not routinely required. Potassium supplementation, erythropoietin, and furosemide do not prevent the tubular damage.

Question 18Medical Oncology: Systemic Therapy and Drug Classes

Which agent is a PARP inhibitor approved for maintenance therapy in platinum-sensitive recurrent ovarian cancer regardless of BRCA status?

  1. Olaparib Correct answer.
  2. Bleomycin
  3. Trastuzumab
  4. Imatinib

Explanation

PARP inhibitors such as olaparib exploit synthetic lethality in cells with homologous recombination deficiency and improve progression-free survival as maintenance in platinum-sensitive recurrent ovarian cancer, including in some patients without BRCA mutations. The other agents are used in unrelated settings.

Question 19Medical Oncology: Systemic Therapy and Drug Classes

A patient with metastatic prostate cancer that has progressed on androgen deprivation therapy is started on abiraterone. Which laboratory parameter requires particular attention?

  1. Platelet count only
  2. Serum potassium and blood pressure Correct answer.
  3. Serum calcium only
  4. Serum amylase

Explanation

Abiraterone inhibits CYP17A1 and suppresses androgen synthesis but also increases mineralocorticoid precursors, causing hypertension, hypokalaemia, and fluid retention. Potassium and blood pressure must be monitored, and prednisone is co-administered. Amylase, platelets, and calcium are not the primary concerns.

Question 20Medical Oncology: Systemic Therapy and Drug Classes

Which immunotherapy-related toxicity requires high-dose corticosteroids and, if refractory, additional immunosuppression such as infliximab?

  1. Grade 3 immune-mediated colitis Correct answer.
  2. Transient fever after infusion
  3. Grade 1 fatigue
  4. Mild pruritus

Explanation

Immune-mediated colitis of grade 3 or higher is managed with high-dose corticosteroids and, if refractory, infliximab or vedolizumab. Low-grade fatigue, pruritus, and infusion-related fever are generally managed supportively and do not require such escalation.

Question 21Medical Oncology: Systemic Therapy and Drug Classes

A patient receiving high-dose cyclophosphamide develops haematuria. Which preventive agent reduces this risk?

  1. Leucovorin
  2. Dexrazoxane
  3. Mesna Correct answer.
  4. Amifostine

Explanation

Cyclophosphamide and ifosfamide generate acrolein, which irritates the urothelium. Mesna binds acrolein in the urine and prevents haemorrhagic cystitis. Leucovorin, dexrazoxane, and amifostine address different toxicities.

Question 22Medical Oncology: Systemic Therapy and Drug Classes

A patient with HER2-positive metastatic breast cancer has progressed on trastuzumab. Which oral agent is a small-molecule tyrosine kinase inhibitor of HER2 that can be used in this setting?

  1. Tamoxifen
  2. Everolimus
  3. Anastrozole
  4. Lapatinib Correct answer.

Explanation

Lapatinib is an oral reversible inhibitor of EGFR and HER2 tyrosine kinases and can be combined with capecitabine in HER2-positive disease after trastuzumab failure. Everolimus is an mTOR inhibitor, and anastrozole and tamoxifen are endocrine agents without HER2 activity.

Question 23Medical Oncology: Systemic Therapy and Drug Classes

In a patient receiving 5-fluorouracil by continuous infusion, which toxicity pattern is most characteristic?

  1. Cardiomyopathy
  2. Pulmonary fibrosis
  3. Mucositis and hand-foot syndrome Correct answer.
  4. Haemorrhagic cystitis

Explanation

Continuous-infusion 5-fluorouracil commonly causes mucositis and hand-foot syndrome, whereas bolus administration is more associated with myelosuppression. Pulmonary fibrosis, haemorrhagic cystitis, and cardiomyopathy are not typical of fluoropyrimidines.

Question 24Medical Oncology: Systemic Therapy and Drug Classes

A patient with non-small cell lung cancer is treated with bevacizumab. Which serious adverse event is specifically associated with this agent and requires urgent evaluation?

  1. Immune-mediated hypophysitis
  2. Cataract formation
  3. Acute pancreatitis
  4. Arterial thromboembolism and haemorrhage Correct answer.

Explanation

Bevacizumab neutralises VEGF and impairs vascular integrity, increasing the risk of arterial thromboembolic events and serious haemorrhage, including pulmonary haemorrhage in squamous histology. Hypophysitis, pancreatitis, and cataracts are not characteristic.

Question 25Medical Oncology: Systemic Therapy and Drug Classes

A patient with metastatic castration-resistant prostate cancer is being considered for a radiopharmaceutical. Which agent delivers beta radiation to bone metastases by targeting prostate-specific membrane antigen?

  1. Lutetium-177 PSMA-617 Correct answer.
  2. Yttrium-90 ibritumomab
  3. Radium-223
  4. Iodine-131

Explanation

Lutetium-177 PSMA-617 binds prostate-specific membrane antigen and delivers beta-particle radiation to PSMA-expressing tumour cells, improving survival in advanced castration-resistant disease. Radium-223 is a calcium mimetic that targets bone stroma without PSMA specificity, and the other agents target different tissues.

Question 26Medical Oncology: Systemic Therapy and Drug Classes

A 58-year-old woman with node-positive breast cancer is planned for adjuvant chemotherapy with doxorubicin and cyclophosphamide. Which monitoring test is most important before each cycle to detect a dose-limiting toxicity of doxorubicin?

  1. Serum creatinine and electrolytes to assess renal function
  2. Pulmonary function tests including DLCO to assess lung diffusion capacity
  3. Audiometry to assess hearing acuity
  4. Echocardiography or MUGA scan to assess left ventricular ejection fraction Correct answer.

Explanation

Doxorubicin causes cumulative, dose-dependent cardiomyopathy, and baseline and serial assessment of left ventricular ejection fraction is recommended, especially when cumulative doses approach 400–550 mg/m² or when cardiac risk factors are present. Renal, pulmonary, and auditory monitoring are not the primary safety checks for doxorubicin.

Question 27Medical Oncology: Systemic Therapy and Drug Classes

A 45-year-old man with metastatic colorectal cancer is receiving FOLFOX (5-fluorouracil, leucovorin, oxaliplatin). He reports new tingling and numbness in both hands and feet that are worse in cold weather. Which agent is most likely responsible for this toxicity?

  1. Oxaliplatin Correct answer.
  2. 5-Fluorouracil
  3. Leucovorin
  4. None of the agents in FOLFOX cause this toxicity

Explanation

Oxaliplatin causes a characteristic cumulative sensory peripheral neuropathy that is often triggered or worsened by exposure to cold. 5-Fluorouracil and leucovorin do not typically cause this cold-sensitive neuropathy.

Question 28Medical Oncology: Systemic Therapy and Drug Classes

A 62-year-old woman with metastatic breast cancer is started on everolimus plus exemestane. Which adverse effect is most characteristic of everolimus and requires regular monitoring?

  1. Hyperthyroidism
  2. Hypoglycaemia
  3. Bradycardia
  4. Stomatitis Correct answer.

Explanation

Everolimus, an mTOR inhibitor, commonly causes stomatitis (oral mucositis), which may require dose modification or topical corticosteroids. It can also cause hyperglycaemia, not hypoglycaemia, and does not typically cause bradycardia or hyperthyroidism.

Question 29Medical Oncology: Systemic Therapy and Drug Classes

A 70-year-old man with metastatic castration-resistant prostate cancer is being considered for cabazitaxel after progression on docetaxel. Which premedication is routinely required before each cabazitaxel infusion?

  1. Intravenous bisphosphonates to prevent bone loss
  2. Antihistamines and corticosteroids to prevent hypersensitivity reactions Correct answer.
  3. Granulocyte colony-stimulating factor to prevent neutropenia
  4. Prophylactic antibiotics to prevent febrile neutropenia

Explanation

Cabazitaxel can cause severe hypersensitivity reactions, so routine premedication with antihistamines and corticosteroids is recommended. G-CSF may be used for secondary prophylaxis but is not a routine premedication for every infusion, and bisphosphonates or antibiotics are not given as premedication for cabazitaxel.

Question 30Medical Oncology: Systemic Therapy and Drug Classes

A 55-year-old woman with metastatic renal cell carcinoma is started on pazopanib. Which baseline and on-treatment monitoring is most important for this agent?

  1. Echocardiography and cardiac troponins
  2. Thyroid-stimulating hormone and free T4
  3. Serum amylase and lipase
  4. Blood pressure and liver function tests Correct answer.

Explanation

Pazopanib, a tyrosine kinase inhibitor, commonly causes hypertension and hepatotoxicity, so blood pressure and liver enzymes should be checked at baseline and monitored regularly. Pancreatic enzymes, cardiac function, and thyroid function are less central to pazopanib monitoring.

Question 31Medical Oncology: Systemic Therapy and Drug Classes

A 68-year-old man with metastatic non-small cell lung cancer is receiving pemetrexed maintenance therapy. Which supplementation is required to reduce pemetrexed-related toxicity?

  1. Vitamin B6 and magnesium
  2. Calcium and vitamin D
  3. Folic acid and vitamin B12 Correct answer.
  4. Iron and erythropoietin

Explanation

Pemetrexed toxicity, particularly myelosuppression and mucositis, is reduced by supplementation with folic acid and vitamin B12. Calcium, vitamin D, iron, and erythropoietin are not routinely given to mitigate pemetrexed toxicity.

Question 32Medical Oncology: Systemic Therapy and Drug Classes

A 50-year-old woman with metastatic breast cancer is receiving trastuzumab emtansine (T-DM1). Which adverse effect is most characteristic and requires monitoring of platelet counts?

  1. Pulmonary fibrosis
  2. Hypertension
  3. Hypothyroidism
  4. Thrombocytopenia Correct answer.

Explanation

T-DM1 commonly causes thrombocytopenia, which is typically transient and nadirs around day 8, so platelet counts should be monitored before each dose. Hypertension, hypothyroidism, and pulmonary fibrosis are not the characteristic toxicity of T-DM1.

Question 33Medical Oncology: Systemic Therapy and Drug Classes

A 60-year-old man with chronic lymphocytic leukaemia is started on ibrutinib. He develops new-onset atrial fibrillation. Which management approach is most appropriate?

  1. Discontinue ibrutinib permanently and switch to another agent
  2. Reduce the ibrutinib dose by 50% and continue
  3. Continue ibrutinib and manage atrial fibrillation with rate control and anticoagulation as indicated Correct answer.
  4. Add a beta-blocker and continue ibrutinib without further evaluation

Explanation

Atrial fibrillation is a recognised adverse effect of ibrutinib. In many patients, it can be managed with rate control and anticoagulation while continuing ibrutinib, especially if the leukaemia is responding and the arrhythmia is controllable. Permanent discontinuation is reserved for severe or refractory cases.

Question 34Medical Oncology: Systemic Therapy and Drug Classes

A 55-year-old woman with ovarian cancer is receiving weekly paclitaxel. She develops numbness and tingling in a stocking-and-glove distribution. Which management strategy is most appropriate?

  1. Increase the paclitaxel dose to overcome resistance
  2. Continue full-dose paclitaxel and add gabapentin for symptom control
  3. Reduce or delay the paclitaxel dose according to the severity of neuropathy Correct answer.
  4. Discontinue paclitaxel permanently and switch to a non-neurotoxic agent

Explanation

Paclitaxel causes a cumulative sensory peripheral neuropathy. For moderate symptoms, dose reduction or delay is recommended to prevent worsening while maintaining antitumour therapy. Permanent discontinuation is reserved for severe or disabling neuropathy, and dose escalation is inappropriate.

Question 35Medical Oncology: Systemic Therapy and Drug Classes

A 65-year-old man with metastatic melanoma is treated with ipilimumab and nivolumab. He develops severe diarrhoea and abdominal pain. Which diagnosis should be suspected first, and what is the appropriate initial management?

  1. Immune-mediated colitis; start high-dose corticosteroids and hold immunotherapy Correct answer.
  2. Infectious gastroenteritis; start antibiotics and continue immunotherapy
  3. Bowel obstruction; proceed to surgery immediately
  4. Irritable bowel syndrome; start antispasmodics and continue immunotherapy

Explanation

Severe diarrhoea in a patient on immune checkpoint inhibitors suggests immune-mediated colitis, which can be life-threatening. The appropriate initial step is to hold immunotherapy and start high-dose corticosteroids, with further immunosuppression if refractory. Infectious workup may be done concurrently, but antibiotics are not the primary treatment.

Question 36Medical Oncology: Systemic Therapy and Drug Classes

A 70-year-old woman with metastatic breast cancer has progressed on anthracycline and taxane therapy and is started on eribulin. Which adverse effect is most characteristic and requires monitoring?

  1. Hypertension
  2. Hyperpigmentation
  3. Pulmonary toxicity
  4. Peripheral neuropathy Correct answer.

Explanation

Eribulin, a microtubule inhibitor, commonly causes peripheral neuropathy, which is typically sensory and cumulative. Hypertension, hyperpigmentation, and pulmonary toxicity are not characteristic adverse effects of eribulin.

Question 37Radiation Oncology: Physics, Techniques, and Indications

A 60-year-old woman with early-stage left breast cancer is planned for whole-breast radiotherapy after breast-conserving surgery. Which technique most effectively reduces the radiation dose delivered to the heart and left anterior descending artery while maintaining target coverage?

  1. Supine positioning with a single en face electron field
  2. Supine free breathing with wide tangential fields
  3. Prone positioning with a photon tangents and no gating
  4. Deep inspiration breath hold with tangential fields Correct answer.

Explanation

Deep inspiration breath hold increases the distance between the breast target and the heart, and the left anterior descending artery moves inferiorly and posteriorly during inspiration, so the cardiac dose falls substantially while tangential field coverage is preserved. This is the most established cardiac-sparing approach in left-sided breast radiotherapy.

Question 38Radiation Oncology: Physics, Techniques, and Indications

In external beam radiotherapy, which statement correctly describes the relationship between absorbed dose and the gray?

  1. One gray equals one coulomb per kilogram of air
  2. One gray equals one joule of energy absorbed per kilogram of material Correct answer.
  3. One gray equals one sievert of equivalent dose in all tissues
  4. One gray equals one hundred rad absorbed in tissue

Explanation

The gray is the SI unit of absorbed dose and is defined as one joule per kilogram. It replaced the rad, where one gray equals one hundred rad. The coulomb per kilogram is the unit of exposure, and the sievert applies a radiation weighting factor and is not identical to the gray in all situations.

Question 39Radiation Oncology: Physics, Techniques, and Indications

Which imaging modality is used at the time of treatment for prostate cancer with implanted fiducial markers to verify target position immediately before each fraction?

  1. Kilovoltage or megavoltage portal imaging of the fiducials Correct answer.
  2. Diagnostic computed tomography performed weekly
  3. Positron emission tomography performed at mid-course
  4. Magnetic resonance imaging performed monthly

Explanation

Daily image guidance with kilovoltage or megavoltage imaging of implanted fiducials allows verification and correction of prostate position immediately before each treatment fraction. Weekly CT or monthly MRI would not provide the daily pre-treatment correction that image-guided radiotherapy requires.

Question 40Radiation Oncology: Physics, Techniques, and Indications

A patient receives 60 Gy in 30 fractions to a tumor. What is the dose per fraction?

  1. 3 Gy per fraction
  2. 1.5 Gy per fraction
  3. 2 Gy per fraction Correct answer.
  4. 0.5 Gy per fraction

Explanation

Dose per fraction is obtained by dividing the total dose by the number of fractions: 60 Gy divided by 30 fractions equals 2 Gy per fraction. This conventional fractionation is typical for many curative regimens.

Question 41Radiation Oncology: Physics, Techniques, and Indications

Which normal tissue is the principal dose-limiting structure when delivering mantle-field or mediastinal radiotherapy for Hodgkin lymphoma at high dose?

  1. The heart and coronary arteries Correct answer.
  2. The skin of the chest wall
  3. The thyroid gland
  4. The humerus

Explanation

Cardiac structures, particularly the coronary arteries, are a major dose-limiting and late-effect concern in mediastinal radiotherapy for Hodgkin lymphoma, with excess cardiac risk documented in long-term survivors. Thyroid and skin effects occur but are less commonly the principal constraint at high mediastinal doses.

Question 42Radiation Oncology: Physics, Techniques, and Indications

Which statement best describes the purpose of a radiation therapy treatment planning system's dose-volume histogram in plan evaluation?

  1. It summarizes the dose distribution within a structure as a cumulative volume receiving at least a given dose Correct answer.
  2. It replaces the need for computed tomography simulation
  3. It measures the actual absorbed dose delivered to the patient during each fraction
  4. It calculates the radiobiological equivalent dose for all fractionation schemes

Explanation

A dose-volume histogram condenses a three-dimensional dose distribution into a curve showing the volume of a structure receiving at least a specified dose, which allows comparison against planning constraints. It is a planning and evaluation tool and does not measure in vivo dose.

Question 43Radiation Oncology: Physics, Techniques, and Indications

In the treatment of a patient with locally advanced cervical cancer, which modality is considered essential alongside external beam radiotherapy for curative intent?

  1. Total abdominal irradiation
  2. Palliative single-fraction radiotherapy
  3. Adjuvant systemic chemotherapy alone without radiotherapy
  4. Brachytherapy Correct answer.

Explanation

Curative treatment of locally advanced cervical cancer combines external beam radiotherapy with concurrent chemotherapy and intracavitary brachytherapy, which delivers the high central dose needed for tumor control. Omitting brachytherapy is associated with inferior local control and survival.

Question 44Radiation Oncology: Physics, Techniques, and Indications

Which radiation modality delivers a steep dose fall-off beyond the Bragg peak, making it attractive for tumors adjacent to critical organs?

  1. Orthovoltage x-rays
  2. Electron arc therapy
  3. Proton beam therapy Correct answer.
  4. Co-60 teletherapy

Explanation

Protons deposit most of their energy at the Bragg peak and stop, producing a sharp distal dose fall-off that spares tissue beyond the target. Co-60 and orthovoltage photons show exponential attenuation without a Bragg peak, and electron arc therapy does not produce a Bragg peak.

Question 45Radiation Oncology: Physics, Techniques, and Indications

A patient with painful bone metastases from prostate cancer is offered palliative radiotherapy. Which schedule is a recognized single-fraction option?

  1. 40 Gy in twenty fractions
  2. 20 Gy in five fractions
  3. 8 Gy in one fraction Correct answer.
  4. 30 Gy in ten fractions

Explanation

A single fraction of 8 Gy is an established and widely used palliative schedule for uncomplicated bone metastases, with pain relief comparable to longer courses. The other listed schedules are multi-fraction regimens and are not single-fraction options.

Question 46Radiation Oncology: Physics, Techniques, and Indications

During intensity-modulated radiotherapy planning for a head and neck cancer, which structure is typically contoured and constrained to limit the risk of xerostomia?

  1. The mandible
  2. The lens of the eye
  3. The spinal cord
  4. The parotid glands Correct answer.

Explanation

Sparing the parotid glands, particularly the contralateral parotid, reduces the risk of radiation-induced xerostomia, which is a key quality-of-life toxicity in head and neck radiotherapy. The lens, mandible, and spinal cord are constrained for other specific toxicities.

Question 47Radiation Oncology: Physics, Techniques, and Indications

Which statement correctly distinguishes the linear quadratic model's alpha/beta ratio for early-responding tissues compared with late-responding tissues?

  1. Early-responding tissues generally have higher alpha/beta ratios than late-responding tissues Correct answer.
  2. The alpha/beta ratio applies only to brachytherapy
  3. Both tissue types have identical alpha/beta ratios of about 3 Gy
  4. Late-responding tissues generally have higher alpha/beta ratios than early-responding tissues

Explanation

Early-responding tissues such as tumors and mucosa typically have alpha/beta ratios around 10 Gy, whereas late-responding tissues such as the spinal cord and lung have lower ratios around 2 to 3 Gy. This difference underlies the greater sensitivity of late effects to fraction size.

Question 48Radiation Oncology: Physics, Techniques, and Indications

In stereotactic body radiotherapy for a peripheral lung tumor, which principle most distinguishes the technique from conventional fractionated thoracic radiotherapy?

  1. Use of low-dose-rate permanent seed implantation
  2. Delivery of a few very high-dose fractions with steep dose gradients and rigorous immobilization and image guidance Correct answer.
  3. Reliance on elective nodal irradiation of the mediastinum
  4. Use of a single large anterior-posterior field without image guidance

Explanation

SBRT delivers ablative doses in a small number of fractions using highly conformal, steep-gradient plans together with robust immobilization and image guidance to account for tumor motion. This is fundamentally different from conventional fractionation with elective nodal coverage.

Question 49Radiation Oncology: Physics, Techniques, and Indications

A patient with a brain metastasis is treated with whole-brain radiotherapy. Which late toxicity is most directly associated with hippocampal dose and can be reduced with hippocampal-avoidance techniques?

  1. Neurocognitive decline, particularly memory impairment Correct answer.
  2. Optic neuropathy
  3. Radiation-induced cataract
  4. Temporal bone osteoradionecrosis

Explanation

Hippocampal dose has been linked to decline in memory and neurocognitive function after whole-brain radiotherapy, and hippocampal-avoidance volumetric modulated arc techniques aim to reduce this dose while maintaining whole-brain coverage. Cataract, optic neuropathy, and bone necrosis relate to other structures.

Question 50Radiation Oncology: Physics, Techniques, and Indications

Which factor most directly increases the penumbra and reduces dose conformality at the field edge in conventional photon radiotherapy?

  1. Increasing the source-to-skin distance
  2. Use of a tissue-equivalent bolus
  3. Use of a higher photon beam energy only
  4. Lateral scatter of photons and electrons in tissue and finite source size Correct answer.

Explanation

The penumbra arises from lateral scatter of secondary electrons and photons in tissue, together with the finite size of the radiation source and collimator geometry. This is why highly conformal techniques require small fields, steep gradients, and careful margin design.