Superficial radiation to ear

[deleted969641]

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80 yo M with multiply recurrent basal cell involving the intratragic notch and concha with positive peripheral margins s/p at least 4 superficial excisions. Small pea sized nodule in the intertragic notch. Plastics finally gave up and referred him to RT.

How would you treat this and dose/fractionation? Target is about a 4 cm circle involving the concha and intertragic notch. Trying to keep dose superficial to avoid IAC and cochlea but unfortunately do not have orthovoltage.
How would you advise patient on risk of hearing loss, cartilage necrosis/ultimate salvage auriculectomy, and acute moist desquamation?

Patient wants to try any chance that avoids losing ear.

I was initially planning on conventional frac to 66-70, but I cannot find good data on it so was going to go 55/22 with 6 MEV electrons plus 1cm ear plug of compensating bolus.

 

[TheWallnerus]

80 yo M with multiply recurrent basal cell involving the intratragic notch and concha with positive peripheral margins s/p at least 4 superficial excisions. Small pea sized nodule in the intertragic notch. Plastics finally gave up and referred him to RT.

How would you treat this and dose/fractionation? Target is about a 4 cm circle involving the concha and intertragic notch. Trying to keep dose superficial to avoid IAC and cochlea but unfortunately do not have orthovoltage.
How would you advise patient on risk of hearing loss, cartilage necrosis/ultimate salvage auriculectomy, and acute moist desquamation?

Patient wants to try any chance that avoids losing ear.

I was initially planning on conventional frac to 66-70, but I cannot find good data on it so was going to go 55/22 with 6 MEV electrons plus 1cm ear plug of compensating bolus.

Electrons fine. Plus allows a 3D sim, and then you know for sure that hearing apparatuses are spared. When I am worried about dose sneaking into the canal, just sim the patient with head in a lateral-looking position and once immobilized for treatment fill the canal to the tippy-top with (room temp) water. You're still going to use bolus in addition to the ear canal (water or whatever plug) bolus. There's no way any of these patients will ever get hearing loss if you use 6 MeV. Although I prefer 9 MeV for all my skin cases. With 1-1.5cm of bolus the dose is ~nil at 2.5cm from the underside of said bolus after all. Treating concha and getting hearing loss as an RT side effect would be malpractice-y. My dose would be 66/33 here but only after you mentioned cartilage necrosis! Technically, we want everyone to get moist desqu in the tx field when treating a skin cancer.

 

[deleted969641]

Electrons fine. Plus allows a 3D sim, and then you know for sure that hearing apparatuses are spared. When I am worried about dose sneaking into the canal, just sim the patient with head in a lateral-looking position and once immobilized for treatment fill the canal to the tippy-top with (room temp) water. You're still going to use bolus in addition to the ear canal (water or whatever plug) bolus. There's no way any of these patients will ever get hearing loss if you use 6 MeV. Although I prefer 9 MeV for all my skin cases. With 1-1.5cm of bolus the dose is ~nil at 2.5cm from the underside of said bolus after all. Treating concha and getting hearing loss as an RT side effect would be malpractice-y. My dose would be 66/33 here but only after you mentioned cartilage necrosis! Technically, we want everyone to get moist desqu in the tx field when treating a skin cancer.

I hear ya, but this got my spidey sense a-tinglin...

theMednet - What dose-fractionation would you use for a recurrent basal cell carcinoma of the right ear concha close to the tympanic membrane status-post multiple Mohs surgeries with close/positive margins?

Why do you think the mednet gurus shyed away from this? I agree and definitely did not feel it was appropriate to deny this man treatment.

Why do you prefer 9E for skin? I don't need a lot of depth and 6E can get there with lower dose to deeper tissues.
Unfortunately I don't have monte carlo so can't model electron dosimetry, but I am planning to CT sim and estimate isodose lines via depth as best I can.

Other question is fractionation. Am I more likely to cause cartilage necrosis with 66/33 or 55/22 or something even more hypofractionated?

Astro skin cancer guidelines are literally all over the place.

 

[communitydoc13]

I've never seen chondronecrosis but in theory its a late effect, thus the longer slower treatment course on ears and nose. Agree with Wallnerus' bolus strategy completely. I use 6mev and not sure why 9 really needed for truly superficial stuff.

Also, basal cell usually behaves itself with XRT. Failure much less likely than with SCC. I would not consent for hearing loss but standard to consent for chondronecrosis.

Regarding Mednet thread, not sure what's going on there. I think maybe they are interpreting the question being a true canal lesion? The concha is not very close to TM (at least not in the adults that I examine) and a BCC of concha a completely different beast than a SCC of the canal, which is a bad bad thing and XRT typically covers whole petrous bone in that situation and yes hearing loss pretty much inevitable.

 

[TheWallnerus]

I hear ya, but this got my spidey sense a-tinglin...

theMednet - What dose-fractionation would you use for a recurrent basal cell carcinoma of the right ear concha close to the tympanic membrane status-post multiple Mohs surgeries with close/positive margins?

Why do you think the mednet gurus shyed away from this? I agree and definitely did not feel it was appropriate to deny this man treatment.

Why do you prefer 9E for skin? I don't need a lot of depth and 6E can get there with lower dose to deeper tissues.
Unfortunately I don't have monte carlo so can't model electron dosimetry, but I am planning to CT sim and estimate isodose lines via depth as best I can.

Other question is fractionation. Am I more likely to cause cartilage necrosis with 66/33 or 55/22 or something even more hypofractionated?

Astro skin cancer guidelines are literally all over the place.

I think the Mednet response was ridiculous. Like someone talking about RT who’s not a rad onc.

re 9 MeV ... just had some physicists through years cast doubt on the 6 MeV relative to other energies. The Lower the electron energy the more the useful dose constricts in from the block edge so you need to probably use a 2cm block margin for the target with 6 MeV. And the 95 to 100 percent range is more peaked and may peak a mm or two more or less depending on the mediums. And perhaps 9 MeV has just a touch better RBE. But 6 MeV is probably fine. I have treated more ears through the years than Dolph Lundgren hung around his neck in Universal Soldier and I have never had necrosis or much less hearing loss. The hearing loss point is cray talk.

As an aside the ability to 3D plan electrons is a real boon to confidence and also quality of care. It shows you things you didn’t know. Also another reason I wind up using 9 MeV a lot. It just looks better than the 6 on screen. Sometimes I hybridize 50:50 for an effective 7.5 MeV beam. These are things you can do with 3D planning of course.

you gotta think. The same cartilage God put in the nasal ala is the same he put in the ear. Treat nasal ala a lot. Never seen a necrosis afaik. Don’t hypofractionate and don’t lose sleep.

 

[metview]

I think the Mednet response was ridiculous. Like someone talking about RT who’s not a rad onc.

re 9 MeV ... just had some physicists through years cast doubt on the 6 MeV relative to other energies. The Lower the electron energy the more the useful dose constricts in from the block edge so you need to probably use a 2cm block margin for the target with 6 MeV. And the 95 to 100 percent range is more peaked and may peak a mm or two more or less depending on the mediums. And perhaps 9 MeV has just a touch better RBE. But 6 MeV is probably fine. I have treated more ears through the years than Dolph Lundgren hung around his neck in Universal Soldier and I have never had necrosis or much less hearing loss. The hearing loss point is cray talk.

As an aside the ability to 3D plan electrons is a real boon to confidence and also quality of care. It shows you things you didn’t know. Also another reason I wind up using 9 MeV a lot. It just looks better than the 6 on screen. Sometimes I hybridize 50:50 for an effective 7.5 MeV beam. These are things you can do with 3D planning of course.

you gotta think. The same cartilage God put in the nasal ala is the same he put in the ear. Treat nasal ala a lot. Never seen a necrosis afaik. Don’t hypofractionate and don’t lose sleep.

I always thought that higher MeV demonstrate more lateral constriction of high isodose levels and more bulging of low isodose levels when compared to lower MeV isodose levels? If true, why does this phenomenon happen? I cant find a good explanation in any of my textbooks/online.

 

[TheWallnerus]

I always thought that higher MeV demonstrate more lateral constriction of high isodose levels and more bulging of low isodose levels when compared to lower MeV isodose levels? If true, why does this phenomenon happen? I cant find a good explanation in any of my textbooks/online.

I might have been inelegant with what I was trying to say. Lateral constriction of high isodose levels with higher energy is true. It constricts in closer to the interior of the block edge if viewing the beam like looking down the barrel of a gun. This is a good thing (with higher energies) IMHO because in our mind's eye we will always equate the area being treated with more or less the block edge. For very low electron energies, the useful dose (ie 80% and higher) at useful depths (ie 2 or 3 cm or shallower), those higher isodose levels constrict in even more, interiorly, from the block edge (again as viewed as looking down the beam as if barrel of a gun). When you are using a smallish field size for an ear with 6 MeV beam, the beginning of the 90-100% lines, and seeing 95%+ of Rx dose, may only start to be seen once traveling 2cm inside the block edge. Anything less than a 4x4 cm field size with 6 MeV is foolhardy physics-wise.

 

[TheWallnerus]

And "hear" is how to treat an ear canal and not risk any hearing loss. Hypothetical case. Ear canal contoured all the way back to TM, and margin (PTV 3mm) on that. Purple is most of the middle/inner ear. Added cochlea after (red). Didn't contour eyes, brain, brainstem; no need.
Rx: 66/33
Needs a little normalization tweak, and this is two summed plans; but still 13 beams only total (all will get a "double shot" the way I planned it).
No hearing loss. No bad moist desqu of external ear. If you trimmed away from the TM a little would all obv look even better.

 

[Neuronix]

This is 6 MV photon? That's clever.

Why not partial arc with 90 degree couch kick instead of all those fixed beams?

We'll ignore that I don't think some of those angles will clear the table/patient. Even if you drop some angles the plan will look pretty similar I suspect.

 

[TheWallnerus]

This is 6 MV photon? That's clever.

Why not partial arc with 90 degree couch kick instead of all those fixed beams?

We'll ignore that I don't think some of those angles will clear the table/patient. Even if you drop some angles the plan will look pretty similar I suspect.

- photon, yes

- They'll all clear 😉 (not first rodeo)

- I didn't have the sunday a.m. patience to optimize and calc the arcs; i did this whole thing in 45 min

 

[deleted969641]

- photon, yes

- They'll all clear 😉 (not first rodeo)

- I didn't have the sunday a.m. patience to optimize and calc the arcs; i did this whole thing in 45 min

I was pondering this as well. Whether I might be able to do better with photon IMRT and make me a little more comfortable since I can see dosimetry with photon and not electron with my TPS. But didn't know how to appropriately plan it.

So you mentioned you favored 9E but it looks like you treated 6X instead of 9E on that case. What leads you to choose photon? Deeper canal lesion in that case?

The other question I'm still not totally clear on is what is the relative risk increase of cartilage necrosis by moderately hypofractionating instead of conventional. I'd really not like to drag this out for 7 weeks if there is not compelling reason why I can't do it in 4. Just theoretical based on a/b of cartilage? My attempts to find any actual evidence are not coming up with much. But thank you, this thread has given me much more confidence. And I agree the mednet question and answers did not make any sense. The concha is not near the TM. And since when is likely moist desquamation an absolute contraindication to RT?

 

[TheWallnerus]

I was pondering this as well. Whether I might be able to do better with photon IMRT and make me a little more comfortable since I can see dosimetry with photon and not electron with my TPS. But didn't know how to appropriately plan it.

Kind of ap/pa and vertex(es) and very nicely placed bolus you can treat the entire external ear (concha, etc) with photons, no reason why not. And spare the tympanic membrane/middle/inner ear almost completely. Many times I will do a hybrid electron/photon and very rarely photon only for skin cancers esp of H&N region. Bolus of some sort obviously very mandatory. I prefer to always scan with a bolus rather than adding fake TPS bolus as I did here. (This is actually an SRS patient who I'm treating a brain met on tomorrow whose images I'm using here for purely illustrative purposes.) Obviously for a whole host of reasons a single non-skin-sparing electron field is preferable most times versus many skin-sparing photon fields, but you can bend the photons to your will too.

So you mentioned you favored 9E but it looks like you treated 6X instead of 9E on that case. What leads you to choose photon? Deeper canal lesion in that case?

I was simply showing, via a fake example, how you could treat the entire ear canal right up to the TM and not have to worry (a lot) about hearing loss. I can't recall I have ever 1) contoured the ear canal before, or 2) treated a real SCC of ear canal. The one I just contoured here was 0.7cc in size (see the inverse optimization GUI above). Not bad for a first try.

The other question I'm still not totally clear on is what is the relative risk increase of cartilage necrosis by moderately hypofractionating instead of conventional. I'd really not like to drag this out for 7 weeks if there is not compelling reason why I can't do it in 4. Just theoretical based on a/b of cartilage?

Purely theoretical.

 

[RSAOaky]

I would imagine surgery in that area is going to result in poor cosmesis with a high chance of requiring adjuvant radiation anyways. In fact, I think it would be safe to say that the likelihood of needing adjuvant radiation is inversely proportional to the likelihood of her keeping her ear. See what you can do to spare her hearing and consent appropriately. Curiously, aside from hearing loss I'm not sure why one of the biggest concerns in that mednet thread is moist desquamation. It's an acute side effect and it will heal...

 

[evilbooyaa]

Yeah MedNet is usually great for practical answers to tough cases, and that H&N doc from Iowa usually has pretty good answers, but I agree that that specific answer isn't a great take when dissected.

I do 50-55/20 on the ear as my go to dose for ear. I don't go faster than that due to concerns about cartilage necrosis, but I treat ear cartilage same as I do nasal cartilage. I've anecdotally seen less acute side effects (not enough follow-up to see any potential necrosis) than the 60-66/30-33 prescriptions of yesteryears.