FRCR FRCR Clinical Oncology 1

Question 1

Which radiation therapy technique allows dose escalation to the tumor while reducing dose to surrounding organs at risk?

Accepted Answer

Intensity-modulated radiation therapy (IMRT)

Answer

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:

Accepted Answer

Cell survival as a function of radiation dose

Answer

The LQ model (S = e^-(αD + βD²)) describes the relationship between radiation dose and the fraction of surviving cells.

Question 3

What is the typical α/β ratio for late-responding normal tissues?

Accepted Answer

~3 Gy

Answer

Late-responding tissues such as spinal cord and lung typically have α/β ratios around 3 Gy, making them more sensitive to large fraction sizes.

Question 4

Stereotactic body radiation therapy (SBRT) is best characterized by:

Accepted Answer

Few high-dose fractions delivered with high precision

Answer

SBRT (also called SABR) delivers ablative doses in 1–5 fractions with sub-millimeter precision using stereotactic localization systems.

Question 5

The oxygen enhancement ratio (OER) in radiobiology refers to:

Accepted Answer

Ratio of dose needed to achieve the same effect in hypoxic vs. oxygenated cells

Answer

The OER quantifies how much more radiation is needed to kill hypoxic cells compared to well-oxygenated cells, typically ~2.5–3 for X-rays.

FRCR - Fellow of the Royal College of Radiologists Practice Test