What margins (CTV and PTV) do you use for boosting breast lumpectomy cavity?

RTOG says:

1. Contour seroma/architectural distortion/relevant clips/lump scar as GTV.
2. Add 1cm expansion for CTV, posteriorly carve til anterior to pec major and don't cross midline; pull into skin 5mm.
3. Add 0.7cm expansion for PTV but exclude heart.
4. Then create PTVeval - pull PTV into skin 5mm, don't cross the midline, and then in vague language protocol says "exclude the Lumpectomy PTV expansion beyond the posterior extent of breast tissue (chest wall, pectoralis muscles, and lung) when pertinent...