6th Annual Brain Tumor Conference: Radio Surgery

Dr. DeSalles - stereotactic radio surgeon
New treatments for brain tumors become widely known in this medical community. He is a neurosurgeon. He believes radiation can help preserve the brain while getting at the tumor. He helps to determine if you have to only radiate the tumor, part of the brain or the whole brain.
Techniques of Stereotactic Radiation
- proton beam (Loma Linda)
- gamma knife - have to give little shots, multiple isocenters
- linac scalpel
- varia 600SR X-Knife
- Cyber Knife (Hoag, USC)
- Novalis - Shaped Beam (UCLA) single is center (conformal radio surgery)
Advantage of Fractions of Radiation (can kill cells in different cycles, have to be done in 30+ session)
Cell cycle advantage more vulnerable during mitosis
Treatment of Brain Tumors:
Surgery
Radiotherapy
Chemotherapy
Immunotherapy


Radiation effect in gliomas and metastases
If tumor is localized you want to focus radiation on it. If malignant glioma with fingers of cells, stereotactic irradiation not best solution. In this case, you would have to radiate a larger area of the brain. With metastatic, we usually have to radiate the whole brain. One singe shot of radiation at high dose is very effective, but so is fractional.

Particle of radiation hits DNA, so cell can no longer divide. It doesn't make tumor vanish, but become sterile overtime and can't reproduce so tumor should decrease. If tumor growing fast, should react quickly to radiation.
If we give fractions of radiation, then we can achieve very high dosage. Novalis can shape the beam to match tumor size. Good for when full resection can't be done or when large areas of tumor can't be radiated (i.e. children).
GBM Results up to date:
Surgery + conventional radiation 9-12 mo survival,
surgery +RT+Temodar 14-19 mo,
Recurrence limited options: chemotherapy: most frequent 5 mo (median)
SRT: 8mo
SRS: 10-11mo

UCLA Approach to GBM
Tumor board
Maximal Resection
Conventional Radiation Therapy (SRT boost)
Chemo: Temodar
Immunotherapy
For recurrent tumors: sterotactic radiotherapy, radio surgery, reoperation, salvage chemo
Clinical trials: vaccine, other chemo agents
GBM
Age is important (may not do surgery in old patients and use sterotactic instead, young patients surgery is 1st option)
When build up amount of radiation (toxicity 90 Gy) we never give more than 60gy. More radiation, you live more, but you can't get the dose too high.
One difficulty is finding where all of tumor is. We have MRI scans, but can't see where invisible cells are, we use PET and MRISpec to show more pathways that we thing we know where the infiltrating tumor cells are.

SRT for Recurrent Gliomas, survival depends on grade of tumor, has marginal importance in the treatment of recurrent, because GBM is a diffused disease. Very selected cases may be helped.

Gliomas are primary tumors (brain cells degenerate to tumor and don't go beyond the brain but can be in spinal cord). Metastases come to brain from other places, blood born which is why the brain gets a lot of metastases. Metastatic tumors don't send out the fingers like GBM, but recur because they move in the blood. Radio surgery first, focused radiation, surgery, fractionated and sometimes whole brain needs radiation. Untreated 1.2 mo, steroids only 2mo, WBRT 4 mo, surgery + WBRT 7-16mo, radio surgery 7-14 months. Age important, where tumor comes from and neurological grade. Treatment: radio surgery then chemo, immunotherapy (can use sterotactic if no other tumor exists) If lesion bigger than 3cm, you start to get pressure in brain and symptoms and tumor needs removed. If lesion smaller than 3cm and no symptoms can use one shot radiation for single lesion. Have to use whole brain radiation when there are multiple lesions throughout the brain, then chemo then surgery. Melanoma, kidney cancer, tissue cancer are radio resistant. Brest/lung can give radiation and they tend to go away. Metastases is usually circular, homogeneity is not an issue, single dose is the choice, 20Gy=110Gy in conventional fractions.

For recurrence: Fraction radiation, resect then radiate tumor bed. If patient has metastatic brain tumor, you have to take care of tumor elsewhere first.

Avoid whole brain radiation. Can make person age several years because brain shrinks. You can usually avoid doing whole brain in metastatic cases. If you do have tumors elsewhere, you should get MRIs to watch for brain tumors and catch them when they are small. Radio surgery is about 25% more costs-effective than surgery and radiation therapy for treatment of brain metastases.

UCLA approach to brain metastases
Surgery if mass effect (stereostactic fractionation or single dose for tumor cavity)
Radio surgery for up to four lesions
Repeat radio surgery if new
Lesion reaches CSF or innumerous lesions (whole brain radiation)
Palliative radio surgery as lesions grow and compromise neurological status
Rarely people die of brain metastases

Radio surgery is treatment of choice for treatment of brain metastases.