When do you add a third field for IMPORT-LOW style partial breast irradiation?

I don’t usually use the 3rd field and treat with min tangent with FIF to improve homogeneity.

If planning to do conformal RT then prefer an APBI dose of 30 in 5 with VMAT technique.

My standard "whole breast" fields are now similar to the approach used in the IMPORT-LOW trial, though more generous - that is, the field borders are placed 4-5 cm beyond the excision cavity, compared to the 2.5-3 cm used in the trial. We commonly add a lightly-weighted anterior oblique to improve h...

The "IMPORT" in IMPORT-LOW stands for Intensity Modulated Partial Organ RT.

It's interesting that in some of the responses above, question answerers are using seemingly non-IMRT techniques... or at the least, not pointing out that the Intensity Modulated Partial Organ RT trial was perhaps allowed to...

I would say, I almost never add a 3rd field. I have seen excellent outcomes and toxicities with mini tangents alone with very low lung and heart doses.