Radiation Pneumonitis Timing — RACP Adult Medicine MCQ

Correct answer: D — Late radiation fibrosis within the treated lung volume

The best answer is “Late radiation fibrosis within the treated lung volume”. Symptomatic radiation pneumonitis usually occurs within weeks to several months and is characterised by inflammatory ground-glass or consolidative change. A stable geometric opacity with volume loss and fibrosis two years later is the late fibrotic phase. Recurrence and infection still require clinical exclusion, but timing and confinement to the treatment field make fibrosis the best explanation.

Reference: Cancer Council Australia: Clinical practice guidelines for lung cancer: https://www.cancer.org.au/health-professionals/clinical-practice-guidelines/lung-cancer