FRCR FRCR Clinical Oncology 2 — Questions and Answers
Question 1: In brachytherapy, what does 'high dose rate' (HDR) mean?
- Dose rate >12 Gy/hour at the reference point (Correct answer)
- Dose rate <2 Gy/hour
- Pulsed delivery over 24 hours
- External beam boost technique
Correct answer: Dose rate >12 Gy/hour at the reference point
HDR brachytherapy delivers dose at rates exceeding 12 Gy/hour, allowing outpatient treatment with no radiation exposure to staff after source retraction.
Question 2: Which lymphoma subtype is most radiosensitive and has the highest cure rate with radiotherapy alone in early-stage disease?
- Classical Hodgkin lymphoma (Correct answer)
- Diffuse large B-cell lymphoma
- Follicular lymphoma
- Mantle cell lymphoma
Correct answer: Classical Hodgkin lymphoma
Classical Hodgkin lymphoma is highly radiosensitive, and early-stage disease is commonly treated with combined modality therapy including involved-site radiotherapy.
Question 3: Proton therapy differs from conventional photon therapy primarily because:
- Protons deposit most energy at the Bragg peak with minimal exit dose (Correct answer)
- Protons scatter more in tissue
- Protons have a lower LET than X-rays
- Protons cannot be focused precisely
Correct answer: Protons deposit most energy at the Bragg peak with minimal exit dose
The Bragg peak allows proton beams to deposit their maximum dose at a specific depth, then stop, dramatically reducing exit dose to tissues beyond the tumor.
Question 4: What is the primary mechanism of radiation-induced DNA damage that leads to cell death?
- Double-strand DNA breaks (Correct answer)
- Single-strand DNA breaks
- Base oxidation
- Protein denaturation
Correct answer: Double-strand DNA breaks
Double-strand DNA breaks are the most lethal form of radiation-induced damage because they are difficult to repair faithfully and can lead to chromosomal aberrations.
Question 5: Total body irradiation (TBI) is most commonly used as conditioning for:
- Hematopoietic stem cell transplantation (Correct answer)
- Palliative bone pain relief
- Brain tumor radiosurgery
- Whole abdominal lymphoma treatment
Correct answer: Hematopoietic stem cell transplantation
TBI eliminates residual malignant cells and suppresses the immune system prior to bone marrow or stem cell transplantation.
Question 6: Which organ is the dose-limiting structure in thoracic radiotherapy, defined by a V20 constraint?
- Lung (Correct answer)
- Esophagus
- Spinal cord
- Heart
Correct answer: Lung
The lung V20 (volume receiving ≥20 Gy) is a critical dose-volume constraint used to limit the risk of radiation-induced pneumonitis.
FRCR FRCR Clinical Oncology 2
In brachytherapy, what does 'high dose rate' (HDR) mean?