Radiation therapy: some facts

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.

Personal Regards,

Nitin Sethi, MD

 

Brain tumors: malignant gliomas

Thank you for sharing your brother’s history with me Franciso, I understand how difficult it must be for you and the entire family. I wish him my very best and please feel free to contact me here if you have any particular questions related to him.

Let me continue a little about the management of brain tumors. Well like I said once we discover a glioma in the brain, we first try to determine its extent in the brain. Tests like CT scan and MRI brain  with contrast (dye) are carried out to determine its boundries. Then the question of staging the tumor arises. At times from the MRI itself one can be reasonably sure that this is a malignant glioma or GBM. GBM is one of the few brain tumors, that can spread to the underside of the brain via the corpus callosum and hence gives rise to what we call a butterfly lesion on the MRI (imagine a butterfly with her wings spread out). GBM usually have a lot of surrounding edema which we can see on the MRI again hinting that is a malignant tumor we are dealing with.

Low grade tumors usually are walled off (encapsulated) and do not much surrounding edema. So the next step is trying to stage the tumor and trying to determine its grade. For this reason at times a brain biopsy is done. At the time of the brain biopsy, a frozen specimen is sent to the lab and if the lab gives its initial impression as a tumor, the surgeon might try to debulk the tumor right then and there (that means at the time of biopsy, try to debulk the tumor. This makes sense because the skull is already open and it avoids a second operation).

There is one issue here which is unique for brain tumors like gliomas. The tumor may have one grade on one side and another grade in a different part of the tumor (meaning one part of the tumor may show grade II and the other grade III. To overcome this problem multiple biopsies are taken from different parts of the tumor. The highest grade found is the final grade given to the tumor).

Like I said earlier depending upon the stage of the tumor and its location, the surgeon may or may not be able to remove the entire tumor.

After the biopsy/ surgery patients undergo rehablitation and are then referred to either radiation oncology for radiation or to an oncologist for consideration of chemotherapy. Most of the times all these facilities are available under one roof in a big hospital.

I shall touch on the finer aspects of radiation and chemotherapy in my next post. Its 7.00 pm sat evening NYC, do not have any major plans but do want to get to the gym at some point. Hope all is well in the big world around me.

Personal Regards,

Nitin

Brain tumors: malignant glioma

Since the diagnosis of Ted Kennedy with a malignant glioma, the focus has again turned to brain tumors. Let me discuss in this post a little about malignant gliomas. Glioma are one of the most common primary brain tumors. They are called gliomas because the tumor arises from the glial cells (the tumor does not arise from neuronal cells, rather from glial cells which form the structural supporting cells in the brain).

The WHO (world health organization) grades gliomas into 4 classes:

1) Grade I and II gliomas: are also what are called low grade gliomas. These are slow growing tumors, usually seen in the younger age groups. As they are slow growing, they are less malignant and compatible with a longer survival. They ususally present clinically with a seizure (when they irritate the underlying brain) or when they grow in size and become large, they present with mass effect (the mass and bulk of the tumor presses on surrounding structures and patients may present with weakness on one side). How are low grade gliomas treated?

Treatment of low grade gliomas; as these tumors are slow growing, they are at times amenable to surgical resection. This is because these tumors are usually well encapsulated and its margins are well defined. So in children or adults, if we catch these tumors in time and if the tumor does not involve the eloquent cortex (parts of the brain which subserve speech, or control the hand and leg movements), one may be able to resect the entire tumor out enbloc. In some patients, that is all what may be needed and we usually like to avoid radiation in children ( since radiation has its own problems and may cause cognitive deficits in the young child later on). You doctor may also put you on an anti-seizure medication for a short while to prevent you from having seizures.

Grade III and IV gliomas: or high grade gliomas. This includes glioblastoma multiforme or GBM. Since these tumors are high grade, they are usually fast growing and invade the surrounding brain tissue. Hence it is impossible to resect the entire tumor out usually. Even if you resect the entire tumor you see macroscopically (that is with the naked eyes), the tumor has already caused microscopic metastasis and spread in the brain. Here in lies the fact why these tumors are so hard to treat and patients usually have a poor prognosis. In the best centers in the world, we treat these tumors with a combination of surgery ( try to debulk the tumor and remove some of it and decrease the pressure in the brain), radiation (you may either radiate just the tumor or irradiate the entire brain to prevent metastatic spread) and chemotherapy. Radiation and chemotherapy may either be used concurrently  to supplement each other or one after the other. Again usually these tumor present at first with seizures and your doctor may start you on an anti-epileptic drug to prevent it.

I shall build on this discussion in my next post. Enjoy the weekend everyone, it is a beautiful day here in NYC.

Personal Regards,

Nitin Sethi, MD