Metastatic Brain Tumors: Radiosurgery – Treatment

by Roy Strowd, MD

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    00:01 What about radiation therapy? How do we think about radiation that second type of treatment for brain metastasis? Well, I'd like for you to think about three types of radiation therapy.

    00:11 The first is stereotactic radiosurgery.

    00:13 This is high dose of extremely focused radiation given to one or several areas of the brain.

    00:19 It has some names. Gamma knife or cyberknife, which are just other words that mean stereotactic radiosurgery.

    00:25 Its focal.

    00:26 It's a high dose delivered to one or several fossa in the brain.

    00:31 It's really good efficacious, and it has limited toxicity.

    00:34 But there is a high rate of recurrence outside of where the radiation is delivered, because it's only delivered to the area where the high dose of radiation is treated.

    00:43 The second type of radiation that I like for you to know is partial brain radiation.

    00:48 This is called intensity-modulated or conformal radiation.

    00:52 We're just a part of the brain is treated with radiation.

    00:55 There is maximal treatment to the area of the tumor, and then some treatment that's delivered to the margin around the tumor that could give rise to recurrence.

    01:03 We don't treat the whole brain and so there's less cognitive risk with that.

    01:06 But we do treat a larger area to prevent recurrence into surrounding areas around the tumor.

    01:12 The last type of radiation is whole brain radiation, where we treat the whole brain.

    01:18 This is one of the oldest forms of radiation, and it's really good for patients who have many metastases, or many tumors on the brain, like the patient in our case.

    01:30 So let's go through each of those types of radiation therapy and see and understand a little more about them.

    01:35 Here we see a good example of the treatment field for stereotactic radiosurgery.

    01:40 You can see the colored images on this slide show where the radiation is delivered.

    01:45 The high doses of radiation are red, and there is very quick fall off or drop of that dose.

    01:51 As we go to areas around where that metastasis is.

    01:54 We can treat the metastasis very well and very specifically.

    01:58 And this is a great treatment for focal brain metastases, for a small number, or a limited number of brain metastases, and preserves patient's quality of life and neurocognition because a lot of the brain is not receiving radiation.

    02:13 There are some advantages and some disadvantages to stereotactic radiosurgery.

    02:17 It effectively treats the disease that we can see on the MRI, but it doesn't treat microscopic disease that could be elsewhere in the brain, and give rise to subsequent metastases.

    02:27 We avoid neurocognitive dysfunction, but we give a high dose to a certain area of the brain and we can see necrosis in the brain that can be challenging to treat, and cause swelling and inflammation around that area of metastasis.

    02:41 <inaudible> Stereotactic radiosurgery can be delivered on a single day really quickly, and avoids delays to systemic treatment, and more intense planning.

    02:51 And we're able to retreat areas or treat new areas of the brain with stereotactic radiosurgery which is not possible with other types of radiation.

    02:59 What about partial brain radiation? This we also called intensity-modulated radiation therapy.

    03:05 This is where a part of the brain is treated with radiation.

    03:08 You can see it here in this treatment planning slide.

    03:11 Again, the area of red is where the high dose of radiation is delivered up to mini gray radiation is measured in gray with a gradual fall off to a margin around the tumor.

    03:22 And you can see that here in the right side of that slide.

    03:24 Again, a high dose of radiation delivered to a large area of the brain to cover both the tumor and the margin around it.

    03:33 And the last type of radiation is Whole-brain radiation therapy.

    03:36 And we can see a treatment plan for treating the whole brain with radiation.

    03:41 This is favorable and good for patients who have too many brain metastases to effectively treat them with stereotactic radiosurgery, when we're worried about subsequent decline in quality of life or neurocognition because the whole brain is treated.

    03:54 And there is a high risk for neurocognitive dysfunction after this treatment.

    03:59 And it's avoided when possible due to side effects.

    04:03 Here we see an example of a whole brain radiation field where we spared the hippocampal.

    04:08 Hippocampal or the areas of the brain that are important in contributing to new memory function.

    04:14 And our field is exploring new ways to give radiation that will treat the metastasis, but not lead to neurocognitive dysfunction.

    04:21 And a good example of that here.

    04:23 So when we do Whole-Brain Radiation Therapy? Well, for tumors that are likely to metastasize widely throughout the brain, like small cell lung cancer, when many metastases exist more than 15 metastases.

    04:35 Patients who have progressed in the CSF space, where we need to treat all of the brain and the multiple compartments around it, and for rapidly progressive brain tumors.

    04:46 Relative contraindications or reasons not to think about whole-brain radiation therapy as if we've radiated the brain before and multiple rounds of whole brain radiation therapy are not possible to the high risk.

    04:57 Cancers that can be targeted with a systemic agent into systemic chemotherapy.

    05:02 Patients who have a low life expectancy or innumerable systemic metastases, which are likely to become problematic, or result in death, and severe impairment in neurologic function obtundation without improvement with corticosteroids.

    About the Lecture

    The lecture Metastatic Brain Tumors: Radiosurgery – Treatment by Roy Strowd, MD is from the course CNS Tumors.

    Included Quiz Questions

    1. High rate of out-of-field recurrence
    2. Treats the whole brain
    3. High rate of post-radiotherapy neurocognitive decline
    4. Can treat microscopic disease not observed on MRI
    5. Relatively inexpensive to perform
    1. Progressive leptomeningeal disease
    2. > 5 brain metastases
    3. Severely obtunded patients showing no signs of improvement after corticosteroids
    4. > 15 brain metastases and innumerable lung metastases
    5. Life expectancy < 3 months due to extracranial disease
    1. Radiation necrosis is a potential side effect.
    2. Treatment requires multiple sessions.
    3. It is poorly efficacious.
    4. It is Indicated if there are more than 15 brain metastases.
    5. After treatment, brain metastases rarely reoccur.

    Author of lecture Metastatic Brain Tumors: Radiosurgery – Treatment

     Roy Strowd, MD

    Roy Strowd, MD

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