Hello everyone, it is Memorial day as I sit down to pen this. Thought since we were on the topic of management of brain tumors, I should give you all some information about radiation therapy. As I stated earlier, radiation therapy is one of the modalities we use in the treatment of brain tumors apart from surgery (debulking the tumor) and chemotherapy (anti-cancer drugs).
So how does radiation therapy work? Well put in a simple form, radiation is given to the tumor to kill the tumor cells. Either you can irradiate the whole brain or just the tumor site. Radiation of the whole brain is done when there are multiple metastasis or when you are worried that microscopic spread of cancer might have already occurred.
Advantages of radiation therapy: one of the biggest advantages of radiation therapy is the ease of administration. Usually you go to a radiation oncology center and it is an outpatient procedure. But we are jumping ahead of ourself. Before radiation is administered, the radiation oncologist in consultation with your neurologist and neurosurgeon shall look at your MRI scans and then determine which shall be the best protocol for you. How much radiation to give over how much time and sittings. Should the whole brain be radiated and then a boost of radiation given to the tumor itself? As you can imagine it is very technical and involved expertise. How to give the radiation without affecting any neighbouring cells (remember radiation by itself cannot differentiate between healthy and tumor cells. It shall kill all cells in its path). If the tumor is near the visual pathways (the optic nerve), then you have to be careful that you do not irradiate the optic nerve as it shall lead to blindness. All such issues are looked at and considered before the protocol is decided.
By studies on animals we now know approximately how much radiation we can safely give to the brain and spinal cord over how much time.
Points to remember: when radiation is started, it leads to death of tumor cells. This increases the edema and swelling in the brain initially. Your doctor may prescribe you steroids or additional steroids if you are already on them to make the swelling go down. Also as the brain swells after radiation, some patients can have seizures and it may make sense to be on an anti-epileptic drug at the time of radiation.
What are the long term side-effects of radiation: Radiation does have some side-effects. In adults and especially in children it can lead to cognitive deficits and affect memory. That is why we try to avoid radiating a developing brain of a child. Also radiation itself at times can lead to a secondary tumor ( we try to avoid this by using the lowest radiation dose as possible). There is an entity called post radiation necrosis which at times can cause some diagnostic problems. About 12-18 months after radiation, necrosis of brain tissue occurs. This at times can present with seizures and be confused with recurrence of brain tumor.
I hope I have been able to shed some light on radiation therapy with respect to brain tumors. It is a lovely Memorial day here in NYC. Plan to head to Central Park and read with the sun on my back. Life is beautiful, I try to remind myself everyday. I wish you all a restful and enjoyable day.
Nitin Sethi, MD