Radiosurgery in brain mets: late recurrences & retreatment options

[Palex80]

Hello, I'd be glad if I could have your input.

I've encountered two patients recently with brain mets, which have been treated previously with radiosurgery and are now recurring with the same treated mets and without evidence of any new mets.

Retreatment of brain mets is something we do quite often after WBRT, there is tons of data on radiosurgery for recurrent brain mets after WBRT. There are also a couple of case series of patients getting a second course of WBRT for multiple recurring mets. And of course WBRT after radiosurgery is not much of an issue.

However I have not found any data on focal re-treatment for previously radiosurgically treated brain mets.

I am looking at two patients, who have both received radiosurgery for 3-4 mets each and 1 of these mets is now progressing around 3 years after the initial radiosurgery. How would you treat that?
Dose was 1x25 Gy in the isocenter. I wouldn't do a second radiosurgery, the risk of necrosis is probably too high. I was thinking of doing something like 10 x 3.5 Gy or 5 x 5 Gy.
The only tumor we have good data on retreatment on in the brain is glioblastoma. Can one assume that 30 x 2 Gy is something like 1 x 25 Gy? In that case, retreating with 5 x 5 Gy or 10 x 3.5 Gy should be safe (plus initially per radiosurgery treated brain volume is certainly smaller than most glioblastoma 30 x 2 Gy volumes).

What do you think?
Is this something we may encounter more often down the road, as more and more patients live longer with stage IV disease? Data on radiosurgery are excellent with >90% local control rates in literature, but follow-up time in the trials seldom goes beyong 1 year.

Thank you for your input.

---

Members don't see this ad.

 

[Gfunk6]

Agree with hypofractionation or conventional fractionation in these scenarios as you've described.

 

[Lamount]

Are the patient's symptomatic?

At my institution, we will sometimes watch patients who are asymptomatic with enlarging brain mets s/p SRS. If the patient is asymptomatic, the lesions are growing slowly, and it's been a long interval since treatment, the growth may represent slowly-evolving necrosis rather than disease recurrence.

 

[Palex80]

Thanks for your input Lamount, that's indeed a very important differential diagnosis. The patients are symptomatic and they do have some edema as well around the metastatic lesions. On the other hand, necrosis can also cause edema.
Nowadays our neuroradiologists can use all kinds of toys (diffusion weighted images, spectroscopy, etc), which can be helpful to differentiate between necrosis and viable tumor in most cases, and they have opted for tumor in both cases. But as you said, if you can't be certain that it's tumor, you can actually wait and see what happens.
I wonder if Avastin would be an option in cases, where you are not quite sure if its necrosis or not. Avastin has proven to be quite active against necrosis, thus if you gave it a couple of times together with steroids and performed imaging again, it may help to differentiate between necrosis and viable tumor.