FRCR Radiobiology 2

Question 1

What is the standard dose per fraction in conventional radical radiotherapy?

Accepted Answer

1.8–2.0 Gy

Answer

Conventional fractionation uses 1.8–2.0 Gy per fraction, balancing tumor cell kill while allowing repair of sublethal damage in normal tissues.

Question 2

Which of the following best describes hyperfractionation in radiotherapy?

Accepted Answer

Multiple smaller fractions per day to increase total dose while limiting late toxicity

Answer

Hyperfractionation uses multiple daily fractions with smaller doses per fraction, exploiting differential α/β ratios to increase total dose and improve tumor control while protecting late-responding tissues.

Question 3

A treatment delivers 2 Gy × 30 fractions to a tumor with α/β = 10 Gy. What is the Biologically Effective Dose (BED)?

Accepted Answer

72 Gy

Answer

BED = nd × (1 + d/[α/β]) = 30 × 2 × (1 + 2/10) = 60 × 1.2 = 72 Gy.

Question 4

Accelerated repopulation of tumor cells during radiotherapy is generally thought to begin after approximately:

Accepted Answer

3–4 weeks

Answer

Accelerated repopulation begins around 3–4 weeks into radiotherapy as surviving tumor cells increase their proliferative rate in response to radiation-induced cell loss.

Question 5

Prostate cancer has an unusually low α/β ratio estimated at approximately:

Accepted Answer

1.5 Gy

Answer

Prostate cancer has an α/β ratio of ~1.5 Gy, similar to late-responding normal tissues, making it particularly sensitive to high dose-per-fraction hypofractionated schedules.

FRCR - Fellowship of the Royal College of Radiologists Practice Test

FRCR - Fellowship of the Royal College of Radiologists Practice Test

FRCR Radiobiology 2