Radiotherapy & Nuclear Medicine · NEET PG Preparation Radiology
What is the primary radiobiological mechanism by which fractionation of radiotherapy enhances the therapeutic ratio between normal tissues and tumors?
Practice question from Radiotherapy & Nuclear Medicine (NEET PG Preparation Radiology), with the correct answer and a step-by-step solution.
hard · MCQ · Q-797C84
What is the primary radiobiological mechanism by which fractionation of radiotherapy enhances the therapeutic ratio between normal tissues and tumors?
- A.Induction of permanent cell cycle arrest in G0 phase
- B.Reassortment, repair, repopulation, and reoxygenationCorrect answer
- C.Irreversible depletion of tumor stem cell niches via direct hyperthermia
- D.Complete elimination of the hypoxic fraction in a single high dose
Solution
The '4 Rs' of radiobiology explain fractionation: Repair of sublethal damage in normal tissues, Reassortment of cells into sensitive phases of the cell cycle, Reoxygenation of hypoxic tumor cells, and Repopulation of surviving cells. Normal tissues typically repair sublethal damage more efficiently than tumors, and tumors benefit from reoxygenation between fractions.
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