How, if at all, has the new DAHANCA H&N contouring guidelines changed how you delineate low dose CTV (CTV-P2) for head and neck cancer primaries?

Should any additional anatomical areas be intentionally included in CTV-P2 if it goes beyond the "5+5" expansion? The text (found here:https://www.ncbi.nlm.nih.gov/pubmed/29180076) states that the PTV-P2 "may" or "likely" extend extend through certain structures but do not specify that these structures should be intentionally included if they go beyond the standard 10mm expansion. Are people in the US dropping anatomy based CTVs (eg for tonsil primaries - ipsilateral soft palate, ipsilateral base of the tongue, ipsilateral glossotonsillar sulcus. Superiorly, ipsilateral pharynx superiorly to pterygoid plate)? Do people stick with these recommendations only for T1/2 and not T3/4?

1 Answer

Mednet MemberInvited Expert

Radiation Oncology · Memorial Sloan Kettering Cancer Center

Answered on

I think it is important to keep anatomical boundaries for head and neck cancer. To depart from that is problematic for the primary disease site. My subclinical region always takes into account the anatomical likely site of spread. The 5 by 5 rule that the consensus guideline referenced is an old schooled way, one may get away with it because a very large volume encompassed by the GTV expansion to high dose causes dose spills into the subclinical regions. I actually do not feel we need a CTV margin for the GTV that is all getting the full GTV dose. A more limited volume of full 70Gy with dedicated subclinical regions based on anatomical boundaries (not only geometric expansion) may reduce toxicity while still getting the necessary dose to the subclinical areas.

I am working on a third edition of my IMRT book where our margins continue to shrink.