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?

The FAST-Forward trial utilized a strict V8 Gy <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 V8 Gy in the 20-25% range in this setting, given the low rates of pneumonitis in the trial, or is failure to meet V8 Gy <15% a strict indication to revert to moderate hypofractionation (40 Gy/15 fx)?

3 Answers

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Radiation Oncology · Varian Medical Systems/Allegheny health network

Answered on

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.

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Radiation Oncology · Emory University Hospital

Answered on

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).

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Radiation Oncology · Jacob E Locke MD PA

Answered on

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.

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