What plan parameters do you prioritize in 3D conformal breast treatment planning?

For whole breast 3D conformal RT, we contour surgical bed with 1 cm expansion for CTV and 3-5 mm for PTV.

Coverage whole breast 95% of volume to 95% of dose we aim for but we accept 90 to 95.

PTV (surgical bed) as above, 95% of volume to 100% of dose but accept 95 to 95 also.
Volume of breast getting 110% of dose is zero.
Volume of breast getting 105% of dose < 10% (< 5% if fast forward) with no105% in IM fold and areola.

No tangential beam going through heart or LAD.

Data for our approach Patel et al., PMID 30145393.

My colleagues' approaches are reasonable. However, I would like to point out that there are few data to know what the optimal dose-fractionation, target goals, or normal-tissue constraints really are. (These issues are dealt with at greater length elsewhere - see Recht et al., PMID 30366007.)

We began routinely using inhomogeneity corrections and three-dimensional compensation using field-in-field forward-planned IMRT for all breast cases at my hospital in 2006. We created an explicit definition of the WB-PTV (defined by the placement of the field borders, so I did not have to spend endless hours contouring the breast) and coverage constraints to give the dosimetrists direction and achieve uniformity within the department between physicians....

We contour cavity, lungs, heart, cord.

With respect to evaluating plan, I typically place 105%, 100%, 95%, and 90% lines on. I look for 95% line to cover breast (I don't routinely contour breast for 3D plans). For RNI cases, I contour IMNs and set SCV +/- PAB fields, and look for 95% coverage of nodal targets, except IMNs where I am ok with 90% line covering.

For tumor bed, in the initial plan, I am looking for something similar to Dr. @Dr. First Last.

For hots, I like minimal confluent 105% and in most cases no 110%.

Agree with @Dr. First Last and @Dr. First Last, but I do contour the breast tissue, that way there is an actual target. If you use the 95% isodose line to create the target, then it is automatically going to meet your coverage goal (by definition).

It doesn't take hours. I timed it and it takes about 90 seconds to contour 7-8 slices starting from superior aspect of breast tissue to inferior. Use brush and go far anterior to breast tissue, interpolate, then pull inside skin 3mm. Still have to contour lump cavity (as described above). Then, dosimetry can use that as their target to set up beam angle.

Otherwise, agree with coverage/heterogeneity goals.