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I don't like SRS for resection cavity.
The local control rates reported are not good in my opinion.
SRS is a technique were usually a lower isodose is prescribed to the edge of the PTV and a higher dose to the middle of the PTV.
This makes sense if you are treating an intact metastatic lesion, it makes no sense however if you are treating a cavity, since the highest risk for remaining cells is not in the middle of the resection cavity but rather on the circular resection margin.
Furthermore I do have some concerns on morbidity. The normal brain tissue around the cavity may be subjected to less favorable blood circulation and with SRS further damaging endothelium the risk of radionecrosis may rise.
We no longer perform WBRT in the postoperative setting after resection of brain lesions with the exception of resected metastasis of SCLC (which itself is very seldom and only happens if brain surgery was performed as an emergency procedure).
We perform postoperative irradiation of the resection cavity, yet not with SRS but with a fractionated stereotactic treatment schedule, delivering a homogenous dose to the PTV (6 x 5 Gy).
We changed our practice around 4 years ago, after more and more data were pointing into this direction.
Anecdotally some of my colleagues report more patients failing with meningeosis neoplastica after stereotactic treatment and blaim the lack of WBRT for this. I think it's more of a bias. Superior local control in the resection cavity and possibly better distant control with more systemic treatment options becoming available (patients with NSCLC live longer nowadays than 5 years ago and NSCLC is major cause for brain mets) means that more patients are going to fail with meningeosis neoplastic down the road.
Recently a working group published contouring guidelines, suggesting to include a generous margin around the adjacent dura in superficially lying resection cavities. We have not adopted this recommendation.
Logically, the next trial should address surgery alone for single brain mets. Some people already advocate it for young patients with breast cancer.
Well this has been partially tested before in the EORTC trial most recently and was not good.
Adjuvant Whole-Brain Radiotherapy Versus Observation After Radiosurgery or Surgical Resection of One to Three Cerebral Metastases: Results of the EORTC 22952-26001 Study
The local failure rate after resection is significantly higher than after radiosurgery. If you add no adjuvant treatment to surgery, half of the patients are going to have a local recurrence. That's an awful lot...
I add 3mm to the resection cavity when doing 6 x 5 Gy and also include part of the dural tail (without "overdoing" it as in the "guidelines"). It's quite hard to distinguish postoperative dural tail (scar) and possibly contaminated tissue / spread around the cavity.
So maruchan and evilbooyaa, you don't do FSRT of the resection cavity?
Personally I am quite biased against RC even in the primary (non-postoperative) setting.
With the exception of small lesions (<1cm), I have been doing more and more FSRT for brain mets.
The Minniti-schedule for example is excellent in my opinion, I have not seen any toxicity and 3 fractions are not that many.
Single-Fraction Versus Multifraction (3 × 9 Gy) Stereotactic Radiosurgery for Large (>2 cm) Brain Metastases: A Comparative Analysis of Local Contr... - PubMed - NCBI
Bear in mind that Patchell did not give 30 / 3... So if you are going to do WBRT based on Patchell, you'd have to do 50.4 / 1.8.
Bear in mind that Patchell did not give 30 / 3... So if you are going to do WBRT based on Patchell, you'd have to do 50.4 / 1.8.
But, but, but fractionation.... Late effects...Good point. I would LOL and then feel really sad if I saw somebody did this to a patient in the current age.
Contouring guidelines for brain cavity? Sounds useful, please share.
My reading of this study is that brain control does not impact overall survival of metastatic patients.
This is upsetting to radiation oncologists.
Logically, the next trial should address surgery alone for single brain mets. Some people already advocate it for young patients with breast cancer.
A caveat regarding the NCCTG study in particular though, they make a note in the manuscript that some of the "local failures" may actually have been radionecrosis or pseudoprogression. So the LC rate may not be quite as bad as their paper suggests.
But why one fraction? ( radiologically there is typically only normal tissue in the PTV with 2mm expansion)Our general practice is to do postoperative SRS to around 15 Gy depending on cavity size. This is based on both Paul Brown's paper (as cited above) and Anita Mahajan's paper (see below: i can't post link because i'm too much of a newb)
Post-operative stereotactic radiosurgery versus observation for completely resected brain metastases: a single-centre, randomised, controlled, phase 3 trial.
But why one fraction? ( radiologically there is typically only normal tissue in the PTV with 2mm expansion)
Oopse sorry neuronix... didn't see that. I scanned the forum a bit too quickly.
I had several pts on NCCTG trial and I thought it mandated 2mm expansion, probably based on Stanford experience that less conformal plans had better local control. Personally, I have seen a lot more heterogeneity in cavity contours than intact brain mets (I am not talking about contouring the dura), but I see a lot of variability on what is perceived as cavity on the MRI. I also agree that when there is a much larger volume of normal tissue in the ptv than tumor, I would conceptually favor a fractionated approach.But why single fraction? I guess it's a preference thing and since I didn't train on GK I'm not single fraction most of the time in this scenario. We know from Minniti that intact tumors >2cm = more necrosis with single fraction and worse oncologic outcome. If post-op cavities are greater than 2cm (which I've never seen them not be) then why not fractionate that too?
I had several pts on NCCTG trial and I thought it mandated 2mm expansion.