Nodal Target Volumes for T2N0 Larynx with 1cm Sublglottic Extension

[The_Fly]

Hey all - I have a patient with a T2N0 bulky larynx cancer with a separate more poorly differentiated component of his SCCa 1 cm into the subglottis. Colleagues and I are disagreeing on the fields. I want to treat to 70 in 1.8s to the primary and cover bilateral II-IV and VI to a LRPTV dose.

How would you all handle this?

Thanks!

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[Palex80]

I am sorry for asking probably stupid questions, but can you describe us a bit more, what the tumor looks like.
Are we talking about a "bulky" cT2 cN0 glottic cancer with minor subglottic involvement, or is this a transglottic tumor with supraglottic involvement as well?
This question plays a major role in defining target volumes.

As far as the fractionation is concerned, IMHO giving 1.8 Gy/d once to 70 Gy is a rather "bad" fractionation. There are numerous studies demonstrating higher local control rates with either moderately hypofractionated therapy using 2.2+ Gy/d once or with hyperfractionated schedules. I would go for one of the two options, probably hyperfractionation (for example 2x1.2BGy/d to 74.4 Gy).

 

[DubZteR]

I am sorry for asking probably stupid questions, but can you describe us a bit more, what the tumor looks like.
Are we talking about a "bulky" cT2 cN0 glottic cancer with minor subglottic involvement, or is this a transglottic tumor with supraglottic involvement as well?
This question plays a major role in defining target volumes.

As far as the fractionation is concerned, IMHO giving 1.8 Gy/d once to 70 Gy is a rather "bad" fractionation. There are numerous studies demonstrating higher local control rates with either moderately hypofractionated therapy using 2.2+ Gy/d once or with hyperfractionated schedules. I would go for one of the two options, probably hyperfractionation (for example 2x1.2BGy/d to 74.4 Gy).

+1 ... that I would go with a 2.2+ Gy / day # scheme.

 

[The_Fly]

+1 ... that I would go with a 2.2+ Gy / day # scheme.

Agreed. I was all wrong in my OP. Meant 1.8s to the LRPTV dose and will go 210s to the PTV70.

I was more interested in getting an assessment of what nodal levels you'd cover. The tumor extends from R TVC, across AC to L TVC and is "bulky" but obviously T2 so arytenoids are working well. There's no SGL involvement. 1 cm of subglottic involvement.

 

[Reaganite]

Agreed. I was all wrong in my OP. Meant 1.8s to the LRPTV dose and will go 210s to the PTV70.

I was more interested in getting an assessment of what nodal levels you'd cover. The tumor extends from R TVC, across AC to L TVC and is "bulky" but obviously T2 so arytenoids are working well. There's no SGL involvement. 1 cm of subglottic involvement.

I had the same question when I first started residency. There are several sites where extension into an adjacent structure can change nodal managment, but at least for t2no glottic laryx that is not the case. Remember the classical field for a t2n0 lesion is a 6x6 field without eni. T2 tumors that originate in the glottis and spread to the sub or supraglottis just don't behave like tumors that originate in either of these sites. The way its been described to me is that the spread in these early glottic lesions tends to be more superficial and hence the risk of invasion of the deep lymphatics is not the same as would be seen with a tumor that originates in the sub or suprglottis and is more deeply invasive. There are several large retrospective studies which address this issue and in general the risk of lymphatic failure in a t2n0 glottic ca is less than 5%. Should be able to find several of them with a quick google search.

 

[Palex80]

I would not cover lymphatics in this case. My gravest concern was supraglottic extension, but since there is none, I am happy with treating only the larynx.
Keep the arytenoids out of the field after 50-54 Gy if you can.

 

[medgator]

I had the same question when I first started residency. There are several sites where extension into an adjacent structure can change nodal managment, but at least for t2no glottic laryx that is not the case. Remember the classical field for a t2n0 lesion is a 6x6 field without eni. T2 tumors that originate in the glottis and spread to the sub or supraglottis just don't behave like tumors that originate in either of these sites. The way its been described to me is that the spread in these early glottic lesions tends to be more superficial and hence the risk of invasion of the deep lymphatics is not the same as would be seen with a tumor that originates in the sub or suprglottis and is more deeply invasive. There are several large retrospective studies which address this issue and in general the risk of lymphatic failure in a t2n0 glottic ca is less than 5%. Should be able to find several of them with a quick google search.

Technically though, aren't you into the true subglottis once you have >5 mm of extension beyond the glottis? there are lymphatics that drain from the subglottis that might be at risk.

It's similar to when you have a bulky T2 glottic with obvious supraglottic involvement. Some would cover bilat levels II-IV in that situation (treat it like an early supraglottic)

 

[deleted4401]

In the large FL series of early stage larynx, the only T2s that have a risk of LN failure approaching 10% is those with vocal cord impairment. Thought is that invasion of the muscle increases of lymphatic involvement. For those with SGL/SuGL extension, very low risk, probably b/c superficial involvement. 6 x 6, 65.25/29 fx or 70 Gy/35 fx/BID on Fridays per DAHANCA.
S

 

[RadRadRad]

"the only T2s that have a risk of LN failure approaching 10% is those with vocal cord impairment."

Always thought it interesting that the most common justification I've heard for adding ENI is extension to supra or subglottic region when the data actually says the opposite. ie those with partial cord fixation actually have the highest risk of nodal involvement.

Another thing to consider is that the classic 6x6 field does include some ENI of level III. This would only matter if you're at an institution that prefers "carotid sparing" IMRT for T2N0 glottic cancer.

 

[r90t]

Ahhhhh, This was one of my oral board questions in 2010.

I said if impaired mobility makes it a t2 then a 6x6 box, however if due to sig. extention, then to consider also nodes. Why? T1 supraglottic, regardless of depth of invasion, technically should include nodes. Examiner liked the answer, because I didn't automatically spit out the wedged 6x6 cm box, flash skin, etc, but instead, gave him the thought process for my answer. We mowed through 8 cases or so.

Also, T2 does not have a 100% cure rate, so it isn't a chip shot with a 6x6 cm box. We saw some of these failures referred from private facilities to the U during residency.