The clinical scenario posted in this question is not rare, since patient compliance or machine issues could result in missing fractions (i.e. treatment break) as originally planned & scheduled in a conventionally fractionated radiotherapy course (including definitive lung CRT that typically aims...

Very complete answer by Dr. @Steve P. Lee. There's an older paper from @Mitchell Machtay and the RTOG that looks at this: PMID 15927409. This would suggest there is some detriment to extending treatment time, though it wasn't a slam dunk here. I would say we also now need to be cognizant of our...