Hello,
We have a case of a 43 yrs old female with metastatic brain mets from inflammatory bilateral breast. Last May we treated 15 brain mets with CK. She had an overall great response, but she now presents with 1 new lesion and 1 lesion with progression. Luckily both lesions are in the Frontal lobe and far from any OARs. We were planning to do 30Gy/5fx. Are there any thoughts on a different approach for prescription in this case? What is your clinics policy with retreatment for brain in regard to dose and normal brain constraints?
Thank you and I look forward to any feedback.
Comments
Hello,
first of all, sorry for the late reply. The first thing we would look at is the time interval to the previous radiotherapy (minimum 6 months) to make sure that it is really progress. This is the case here in any case.
The fractionated approach would also be our choice for the metastasis that has already been irradiated. In this case, we would tend towards 3 x 9 Gy. However, 5 x 6 Gy is also ok and we also did this in the beginning (BED10 is similar: 51.3 Gy vs. 48 Gy).
Since the unirradiated metastasis is far away, we would rather irradiate it with 1 x 20 Gy (BED10 60 Gy). In both cases, we would prescribe the 75% IDL.
If 2 isocenters / 2 plans are not an option, the unirradiated metastasis can of course also be fractionated.
Thank you for sharing this interesting and challenging case, and sorry for the late response.
Given that the patient had the new and progressive lesions located in the frontal lobe and away from critical structures, your plan of 30 Gy in 5 fractions seems quite reasonable, especially as it balances efficacy with a conservative approach for normal tissue tolerance in a re-irradiation setting.
At our center, for retreatment with SRS/SRT, we typically assess several factors: prior cumulative dose to the brain, the interval since the last treatment (always more than 6 months), and the location/volume of the recurrent lesions.
For lesions far from OARs, we’re comfortable with a second course in the range of 30 Gy in 5 fractions, particularly if the prior dose was delivered months earlier. For the new lesion we could also prescribe 20 Gy in single fraction, but considering th proximity of both lesions I would suggest un single isocenter both both with the same fractionation (30 Gy in 5 fractions)
For normal brain constraints, we generally keep an eye on the V20 (volume of normal brain receiving ≥20 Gy), aiming to keep it under 20 cc per course, and try to limit cumulative V20 across both treatments as best we can.
I hope it helps.