Sciatic Schwannoma

[fiji128]

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I have a patient coming in with a biopsy proven schwannoma of the greater sciatic foramen. It measures 4.7 x 3.6 x 3.2 cm and is symptomatic. How would you treat something of this size/location assuming surgery is not an option.

 

[TheWallnerus]

I don’t ever favor RT as a primary tx for schwannomas due to malignant transformation risks. Would only do if surgery has been completely ruled out. Otherwise, ultra conformal 54 to 60 Gy in 30 fx.

 

[BobbyHeenan]

Probably fractionated radiosurgery, maybe 30-35 Gy in 5. Usually I'd let the middle get really hot, but ?I guess? there would be concern about nerve injury, so I'd probably not heat this one up (and sacrificing more gradual fall off should be OK, I don't see adjacent bowel or anything scary.

interesting case - interested to see what others would do.

something like 50-54 Gy in 25-28 isn't "wrong" either and would be fine by me too.

 

[Palex80]

Otherwise, ultra conformal 54 to 60 Gy in 30 fx.

Does one really need doses >54 Gy for this?
I'd have probably treated 50-54 Gy, or even slightly hypofractionate.

 

[OTN]

30 in 5 or 5040 in 180s

 

[medgator]

I don’t ever favor RT as a primary tx for schwannomas due to malignant transformation risks. Would only do if surgery has been completely ruled out. Otherwise, ultra conformal 54 to 60 Gy in 30 fx.

Surgery seems like it would be pretty morbid here I would think. Id favor conventional or slight hypo given the nerve tissue

 

[Gfunk6]

I've treated a few of these over the years to ~30 Gy/5 fx with excellent local control and symptomatic relief All such patients were seen by Neurosurgery first and deemed not good surgical candidates - not because of age/co-morbidities but rather neurologic complications of resection (e.g. permament foot drop). Malignant transformation after radiation is very rare; patient's should be informed of all risks but this is pretty remote.

 

[radiation]

To my knowledge, the biology of schwannomas are independent of the nerves they arise from so you should be able to extrapolate the data for vestibular schwannomas and give fairly moderate doses like 12-15 gy single fraction or 25-30 gy in 5 fractions depending on your risk tolerance for nerves.

As for the risk of malignant transformation from radiation, per Pittsburgh "in our 32-year institutional experience of over 1950 VS and 16,030 SRS patients, we have not confirmed a case that fulfills the Cahan criteria of a radiation related tumor"

Long term results of primary radiosurgery for vestibular schwannomas - PubMed

In this report with extended follow-up, primary SRS achieved tumor growth control in 94% of patients. Optimization of long- term cranial nerve outcomes remains an important achievement of this management strategy for VS.

pubmed.ncbi.nlm.nih.gov

 

[RickyScott]

I have treated these 50-54 gy w/pain relief in both cases.

 

[Neuronix]

25-30/5 fractions for well circumscribed inoperable tumor.

The dose intracranially is 12/1 which is more or less the same as 25/5.

The question is what can the cauda equina/sacral plexus tolerate, and TG-101 just makes some stuff up that makes it look like 30/5 is unsafe. I've done 27.5/5 for this reason as well.

They can pseudoprogress after treatment. My experience with pain relief has been mixed. Maybe fractionated would be better from that standpoint, at which point 50/25 to 54/27 should be adequate.

I don’t ever favor RT as a primary tx for schwannomas due to malignant transformation risks. Would only do if surgery has been completely ruled out. Otherwise, ultra conformal 54 to 60 Gy in 30 fx.

Is this a thing outside of NF2? Anyway the ones I've had sent to me are either surgical nightmares or elderly, so RT is still the preferred option even with secondary malignancy risk.

 

[NotMattSpraker]

Not aware of any data to suggest malignant transformation with radiotherapy treatment. I would love to see it if someone has any. Data from low grade gliomas could be borrowed to argue this is a myth that could be debunked.

There is likely a low rate of spontaneous transformation without any treatment. This would be most likely in NF, so they should be screened for that. However, I have seen cases of MPNST arising in schwannoma in non-NF patients too.

Most cases in the literature are in non-NF patients.

The argument for surgery is more long term control over protection from malignant transformation in my opinion.

I tend to favor SBRT over conventional fractionation, but there is data to support both.

Control rates are great, but follow up is often relatively limited in studies.

 

[gvsudew]

25-30/5 fractions for well circumscribed inoperable tumor.

The dose intracranially is 12/1 which is more or less the same as 25/5.

The question is what can the cauda equina/sacral plexus tolerate, and TG-101 just makes some stuff up that makes it look like 30/5 is unsafe. I've done 27.5/5 for this reason as well.

They can pseudoprogress after treatment. My experience with pain relief has been mixed. Maybe fractionated would be better from that standpoint, at which point 50/25 to 54/27 should be adequate.



Is this a thing outside of NF2? Anyway the ones I've had sent to me are either surgical nightmares or elderly, so RT is still the preferred option even with secondary malignancy risk.

Some great thoughts here. Having treated alot of these I've had great results with 25-30 Gy hfSRS but definitely see more pseudoprogression in the 2-6 month range with this approach as compared to conventional FX sometimes requiring low dose steroids to control slightly worsening symptoms over that time frame. Incidentally there is often more post RT internal hypointensity on post contrast T1 (presumably necrosis) also and a better chance for (partial) regression at 6-12 months in these same pts.

 

[thesauce]

How old? Probably standard frac up to acoustic neuroma dose

 

[fiji128]

How old? Probably standard frac up to acoustic neuroma dose

Pt is in her mid 70's with an ECOG of 0 to 1. Pt presented with issues of pain presumably due to the mass but otherwise neurologically intact with no weakness.

 

[evilbooyaa]

25/5 safe to equina, should be fine for LC given that's what we'd use for a large intracranial acoustic.
Whether 50-54 in 25-30fx would be better for pain relief, IDK, would be not unreasonable either.

We treat acoustic neuromas all the time in the brain. Worry about malignant transformation is.... not routinely a consideration. Surgery is going to be morbid for this, especially if the surgeons tell you so