What is an acceptable upper limit for ipsilateral lung V8 Gy when using the FAST-Forward regimen with high tangents to cover limited axillary disease?

I would say ipsilateral V8 is more for the ALARA principle and not based on risk of Pneumonitis, and thus would accept a higher number to cover low axillary if needed.

The UK FAST-Forward nodal sub-study (covering axillary levels I-IV without IMN coverage) permitted an ipsilateral lung V30% of up to 25% and reported comparable rates of symptomatic lung fibrosis (2%) at 5 years for both the 40 Gy/15 Fx and 26 Gy/5 Fx schedules (Brunt et al., PMID 40379410).

What % of USA nonacademic practices use 5-fraction whole-breast regimens? I'm gonna go with less than 3%. I'm gonna guess 75% use moderate hypofrac, but I wonder if even that is too optimistic.