What techniques do you typically use for a photon breast boost?   

Depends on the location of the cavity and depth, and breast anatomy. Mini tangents work well but can have a lot of doses beyond boost volumes. I sometimes will use a 3 field approach with a lightly waited anterior electron/photon field depending on the depth of the cavity.

We try to avoid a photon boost if possible to reduce the integral dose to the breast which has an adverse effect on cosmetic outcomes.We try to repeat the scan in the lateral decub position to make it suitable for electrons:Kannan et al., PMID 23006598If we still need photons, we try to use three fi...

If lumpectomy_PTV not amenable to coverage with 6-9mev electrons due to depth, my go-to is a 3 field arrangement with mini-tangents and orthogonal beam. Goal to keep the dose in normal breast tissue beyond PTV to <50% isodose line.