What is an acceptable upper limit for ipsilateral lung V8Gy when using the Fast Forward regimen with high tangents to cover limited axillary disease?  

The Fast Forward trial utilized a strict V8Gy < 15% constraint for whole breast irradiation. However, in clinical practice for patients with N1mi or limited nodal disease requiring high tangents (Level I/II coverage), meeting this constraint often compromises target coverage.

Is it clinically acceptable to accept a V8Gy in the 20-25% range in this setting given the low rates of pneumonitis in the trial, or is failure to meet V8Gy < 15% a strict indication to revert to moderate hypofractionation (40Gy/15fx)?