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Radiation treatment plan

Updated: Oct 11, 2019


The location of the two tumors at the back of David's head in the cerebellum. The largest tumor is about an inch in diameter.

David, his sister Penny, and I met with Dr. David Vonk, the radiology oncologist, on 10/8 to discuss the stereotactic radiosurgery treatment plan. He was extremely nice and did a great job of explaining the process.


Before the treatment can start, the following preparation needs to be done:


  • A plastic mesh face mask needs to be molded to fit David's face and head. David will wear this during the radiation to keep his head from moving. (Apparently, in the past, they had to use screws to keep patients' heads immobile. So although Dr. Vonk said wearing this mask won't be comfortable, it is preferable to that!) A CT scan is done while David wears the mask.


  • David needs to get a high-precision MRI to pinpoint exactly where the three tumors are, so Dr. Vonk knows where to aim the radiation beams. During the treatment, the MRI is overlaid on top of the CT scan to enable Dr. Vonk to target the cancer cells while avoiding damaging surrounding tissue. Because the cancer is growing, radiation needs to be done ideally within a week and no later than two weeks after the MRI is done; otherwise, the MRI will no longer be accurate enough.


  • David will meet with Dr. Eric Sipos, a neurosurgeon who will be working with Dr. Vonk.


With luck, all of these tasks will be done no later than the end of next week, so treatment can start the following week. Because these tasks are time-sensitive, we won't have much say in when they are scheduled or how much advance notice we will get. I will add new posts to this blog as we learn more.


Treatment will consist of five daily radiation sessions, each of which will take about two hours. The largest tumor in the cerebellum and the adjacent smaller tumor will be treated each day, but the smallest tumor (on the top left of David's head) will be treated on only one day.


Dr. Vonk said David won't feel the radiation, but he could get a headache from wearing the mask. Other side effects could include localized hair loss and scalp irritation. Radiation necrosis—the death of healthy tissue that is caused by the radiation therapy—is a more serious possible side effect, but Dr. Vonk said it is rare.


As far as prognosis goes, there is good news and bad news. The radiation is to control the growth of the tumors; it should stop the tumors from growing and could possibly shrink them. But it will not cure the cancer, and more brain tumors may develop in the future, for which additional radiation could be done. Dr. Vonk said he has patients he has worked with for years that he has treated several times.


Also, the treatment might reduce the balance and nausea problems David is having, but it might not if many nerve cells have already been killed in the cerebellum. If only some nerve cells have been killed, other nerve cells might be able to take over for them. Dr. Vonk stressed that it is important for David to keep taking the steroid pills Dr. Brooks prescribed; they will reduce inflammation in the brain, which will reduce pressure in the tissue surrounding the tumors and reduce the chance of nerve cell damage. David plans to keep taking the pills in spite of the awful insomnia they are causing (he's getting only three or four hours of sleep per night, but we hope that increases as his body adjusts to being on the steroids).


After the treatment is done, David will be tapered off the steroid pills, and he will get a new MRI done every two months for a year to check whether any new tumors have formed.


Dr. Vonk provided some interesting facts. One is that David does not have brain cancer per se; he has stomach cancer that has spread (metastasized) to the brain. The other is that the Blood-Brain Barrier (BBB)—blood vessels that allow essential nutrients to enter the brain while blocking other substances from entering the brain prevents chemotherapy drugs from effectively entering the brain. But all it takes is one cancer cell to slip past the BBB for tumors to start growing in the brain. So that's how the stomach cancer spread to his brain and why the IV chemo did not prevent that from happening.


Also, we received the results of his latest CEA tumor marker yesterday. It's up a bit from last time, from 2.4 to 2.9, but that's still in the normal range. So obviously this marker does not reveal everything about the state of the cancer's growth or whether it is spreading.


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