10+ Year Member
- Feb 8, 2008
- Attending Physician
How do you compensate for breathing motion with VMAT? This has come up whenever we entertain VMAT for difficult cases... how do you replicate the flash that you get form standard 3D plans? If the answer is breath hold, there is still considerable variability depending on the threshold that you accept. I am genuinely curious about this because I've never heard an answer that makes me feel OK with VMAT.I am all ears too.
My main concern is that we are indicating IMN-RT based on evidence produced by MA20 and the EORTC trial, which irradiated with very "generous" field arrangements, but are allowing underdosing at the same time. Will the (small) benefit shown in these trials still materialize?
That's how its defined in a large trial we currently have running (over 1600 patients to be recruited):
CTV-IMN (internal mammary nodes):
This volume connects cranially to the CTV-"medial supraclavicular nodes" and includes include both the internal mammary
vein and artery with a 5 mm margin. Dorsal border is the pleura. Caudally this volume ends at the cranial side of the fourth rib,
in case of caudal/medial located tumor at the cranial side of the fifth rib.
For the planning target volume (PTV) an additional margin is to be added to the respective CTV in
order to take intra-fraction, inter-fraction motion and machine uncertainty into account.
These margins depend on institutional standards. Generally, the minimum of 5 mm CTV-to-PTV
expansion is recommended.
For planning reasons the PTV should be cropped 2-3 mm beneath the skin in case of breast
conserving surgery and 2 mm beneath the skin in case of post-mastectomy radiotherapy. In case
of skin involvement the ventral border expands to the skin surface.
Yes we are.