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What happens if you accept focally involved margins ?
Results in the Netherlands:
Vos et al, 2017
N = 1078 with focally involved margins
(out of 10.433 patients treated 2003-2008,
and of whom resection margins were known
(total treated 32.119 patients))
5 yr LR no re-excision + boost: 2.9%
5 yr LR with re-excision +/- boost : 1.1%
This difference is statistically significant,
but clinical relevance doubtful, since:
No effect on 5 yr DFS and 5 and 10 yr OS