FRCR FRCR Clinical Oncology 1 ā Questions and Answers
Question 1: Which radiation therapy technique allows dose escalation to the tumor while reducing dose to surrounding organs at risk?
- Intensity-modulated radiation therapy (IMRT) (Correct answer)
- 2D conventional radiotherapy
- Orthovoltage therapy
- Total body irradiation
Correct answer: Intensity-modulated radiation therapy (IMRT)
IMRT uses multiple beams with varying intensities to sculpt dose around the tumor while sparing adjacent critical structures.
Question 2: In radiobiology, the linear-quadratic (LQ) model describes:
- Cell survival as a function of radiation dose (Correct answer)
- Tumor growth kinetics
- Oxygen enhancement ratio
- Repopulation during fractionated radiotherapy
Correct answer: Cell survival as a function of radiation dose
The LQ model (S = e^-(Ī±D + Ī²DĀ²)) describes the relationship between radiation dose and the fraction of surviving cells.
Question 3: What is the typical Ī±/Ī² ratio for late-responding normal tissues?
- ~3 Gy (Correct answer)
- ~10 Gy
- ~1 Gy
- ~20 Gy
Correct answer: ~3 Gy
Late-responding tissues such as spinal cord and lung typically have Ī±/Ī² ratios around 3 Gy, making them more sensitive to large fraction sizes.
Question 4: Stereotactic body radiation therapy (SBRT) is best characterized by:
- Few high-dose fractions delivered with high precision (Correct answer)
- Daily fractions over 6ā8 weeks
- Whole-organ irradiation at low doses
- Brachytherapy implantation
Correct answer: Few high-dose fractions delivered with high precision
SBRT (also called SABR) delivers ablative doses in 1ā5 fractions with sub-millimeter precision using stereotactic localization systems.
Question 5: The oxygen enhancement ratio (OER) in radiobiology refers to:
- Ratio of dose needed to achieve the same effect in hypoxic vs. oxygenated cells (Correct answer)
- Ratio of oxygen concentration in tumor vs. normal tissue
- Enhancement of dose by radiosensitizers
- Proportion of cells in S-phase
Correct answer: Ratio of dose needed to achieve the same effect in hypoxic vs. oxygenated cells
The OER quantifies how much more radiation is needed to kill hypoxic cells compared to well-oxygenated cells, typically ~2.5ā3 for X-rays.
Question 6: Which chemotherapy agent is most commonly combined with radiotherapy as a radiosensitizer in head and neck cancer?
- Cisplatin (Correct answer)
- Carboplatin
- Paclitaxel
- Gemcitabine
Correct answer: Cisplatin
Concurrent cisplatin-based chemotherapy with radiotherapy is the standard of care for locally advanced head and neck squamous cell carcinoma.
FRCR FRCR Clinical Oncology 1
Which radiation therapy technique allows dose escalation to the tumor while reducing dose to surrounding organs at risk?