Split field vs whole neck IMRT?

[napoleondynamite]

So I was taught on my H&N rotation in residency to, whenever possible (i.e. a cN0 neck, not splitting through GTV, etc) do split field with an LAN rather than whole neck IMRT. I have heard arguments on both sides and some feel that whole neck IMRT can achieve the same goals with a hard constraint on the larynx. In my mind, these are the potential advantages to LAN:

1) Potential for improved laryngeal sparing with midline block, etc. I've seen a couple of papers that have compared IMRT to split field that report minimally improved, but nonetheless improved laryngeal doses with LAN.

2) Dose heterogeneity less with split field technique, easier to achieve fewer hot spots in the plan than with a large IMRT field.

Thoughts? I'm doing a locums gig and my dosimetrist is fairly new so has really only done IMRT and not very comfortable with split field. I went to evaluate the plan and there were 15-20% hot spots at the match line. I should have paid more attention in physics because I'm not sure how to correct her problem. I think in this one case I will just do IMRT since that is what this clinic is most familiar with and comfortable with. But would love a little insight..

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[deleted4401]

You seem to understand it just fine:

Pros of LAN - spare larynx, potentially more homogeneous dose.
Cons of LAN - have to match which leads to match issues (hot and cold spots, match-line fibrosis) and increases complexity of treatment (ask the physics/therapists, they really seem to hate it).

Our training biases can make us dogmatic. I learned the other way - IMRT throughout, and thought about doing a low neck match because of the potential for larynx sparing, but was convinced otherwise by physics and I couldn't find evidence of a clinical benefit. The Florida group had something in PRO about this, and basically said with tighter constraints, no need to do the match: http://www.practicalradonc.org/article/S1879-8500(10)00005-6/abstract.

S

 

[medgator]

There's a few papers in wikibooks on this topics. Seems to be institutional preference and/or the specific clinical scenario when going with a LNF.. I find it most feasible to do IMRT the whole way and contour the larynx/pharyngeal constrictors as an avoidance structure.

http://en.wikibooks.org/wiki/Radiation_Oncology/Toxicity/Larynx

Edit: Saw SimulD's post above. The original UF paper is here: http://www.ncbi.nlm.nih.gov/pubmed/14999801?dopt=Abstract

 

[Gfunk6]

I use IMRT all the way. Make sure you contour the larynx and esophagus and use conservative mean dose restrictions. Generally if your treatment planning staff is not familiar with a certain technique it is best not to "learn on the fly."

 

[napoleondynamite]

Thanks everybody. Ya know, I feel like the learning is just beginning. It's one thing to follow along with your attendings patients, another to actually be steering the ship. But I think I will remember these lessons now that I'm in the hot seat!

Anyway, thanks to all for your thoughts on this.

ND

 

[SneakyBooger]

IMRT the whole neck...

 

[Reaganite]

So I was taught on my H&N rotation in residency to, whenever possible (i.e. a cN0 neck, not splitting through GTV, etc) do split field with an LAN rather than whole neck IMRT. I have heard arguments on both sides and some feel that whole neck IMRT can achieve the same goals with a hard constraint on the larynx. In my mind, these are the potential advantages to LAN:

1) Potential for improved laryngeal sparing with midline block, etc. I've seen a couple of papers that have compared IMRT to split field that report minimally improved, but nonetheless improved laryngeal doses with LAN.

2) Dose heterogeneity less with split field technique, easier to achieve fewer hot spots in the plan than with a large IMRT field.

Thoughts? I'm doing a locums gig and my dosimetrist is fairly new so has really only done IMRT and not very comfortable with split field. I went to evaluate the plan and there were 15-20% hot spots at the match line. I should have paid more attention in physics because I'm not sure how to correct her problem. I think in this one case I will just do IMRT since that is what this clinic is most familiar with and comfortable with. But would love a little insight..

My head and neck attending did split field with a gradient match technique (3 separate match lines) and our planners absolutely hated it. They'd spend days optimizing that damn match line. It was horrible really. I've done locums at several places and rotated at several hospitals outside my institution, and I've yet to see anyone do it this way. They all did whole field imrt and just constrained the hell out of the larynx.