Breast SCV prescriptions?
Started by ShirleyT
Does anyone still use Rx points anymore in this day and age of CT-based planning and 3DCRT?
D
deleted4401
Contour the SCV and level III nodes. Cover the volume with 45 or 46 Gy depending on fractionation scheme. Dose by depth or Dmax will over/underdose in a significant number of patients. Not sure if it matters clinically, as rate of recurrence is so low to begin with, but if you're gonna treat, you might as well treat.
I contour SCV/Level III LNs and use control points for optimal coverage. Since you are using a single anterior oblique beam most of the time, you are limited to what you can realistically achieve.
Like ShirleyT, I accept 45 Gy for deep LNs in most situations. I don't like to fry anterior structures in an attempt to squeeze in 50 Gy to all level III LNs.
Like ShirleyT, I accept 45 Gy for deep LNs in most situations. I don't like to fry anterior structures in an attempt to squeeze in 50 Gy to all level III LNs.
So we use this philosophy and do things slightly differently. We start by contouring all our target structures including ICV/SCV. Planning starts with the usual half-beam blocked, monoisocentric technique for the breast with iso set at the bottom of the clavicular head.
With regards to the ICV/SCV field, the conventional teaching is the third anterior field prescribed to a depth as Gfunk just mentioned. This works fine for thin people, but as he mentions, you can only get in so deep with an anterior only beam.
So we do it in four fields, adding an opposed posterior beam to the conventional three field technique. Typically for the SCV fields, this is 6MV PAO/APO. This way we can achieve a homogeneous 50 Gy easily to the contoured nodal volume. Of course, it probably makes no clinical difference, but the plans look nice.
That's usually what I end up doing as well. Simply prescribing to a point ends up underdosing (more often than overdosing) what you've delineated on your CT. I agree with others that I am happy with 45 Gy to these nodal regions unless there is involvement.
We'll treat to 50Gy if we can get it, but skimp down to 45Gy sometimes if needed for constraints. It depends on the circumstances. This most often comes up when doing elective IMN irradiation to spare lung and heart dose.
Precisely our approach too. Feels good to know, that other people are doing the same!
