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Radiology · Radiotherapy: hyperfractionation
Sample itemIn a hyperfractionated schedule, smaller doses are given two or more times daily. What biological principle makes this attractive?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
B. Late-responding normal tissues are spared more by small fractions, permitting a higher total dose
Late-responding tissues are highly sensitive to fraction size, while tumours and acute-reacting tissues are less so. Small fractions therefore protect late tissues, so a higher total dose can be delivered for the same late toxicity.
Option by option
A. The total number of fractions is reduced
Hyperfractionation increases the number of fractions.
B. Late-responding normal tissues are spared more by small fractions, permitting a higher total dose (correct)
Correct. Small fractions favour sparing late-responding tissues.
C. Tumour cells repair damage better between fractions
Repair favours normal late tissue, and tumour repair is not the intended gain.
D. Acute-responding tissues become more resistant
Acute tissues are not made resistant, and acute toxicity may rise.
Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.
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