However, there is about a 1 in 50,000 chance that the radiotherapy treatment can turn the benign AN into a malignant tumor. Odds are high but still a worry.
This post is a classic example of the emotive fears of radiation. I guess maybe we've all lived in fear of nuclear war in these times and the very word radiation can be frightening. However, radiation has been used in medicine long before it was used as a weapon, it's a very powerful thing, but it can help as well as hurt. Let's all look closely at the statement above. Larry is trying to make a decision between another surgery and radiosurgery, and is worried about a 1 in 50,000 chance of malignant transformation. Why isn't he alot more worried about the 1 in 100 chance of immediate death on the operating table? In the extremely unlikely event of malignant transformation, there is still the possibility of surviving the malignancy, whereas there is no chance of surviving when you die on the table. Also, there is no evidence that radiosurgery even caused the malignant transformation in the very few cases that have occured, because just about an equal small number of malignant transformations have occured following surgery, with no radiation whatsoever. Some doctors believe there is actually no such thing as malignant "transformation" in schwannomas, but that they had a malignant element the whole time. In schwannomas, very rarely they can have small pockets of malignant cells that can be missed when biopsied, so it's hard to say surgery or radiation caused it to become malignant, when it may have been malignant the whole time.
I would love to see a formal study done if anyone has one.
There have been so few cases, that would be difficult. But here's the closest thing I could find for you:
http://www.anarchive.org/malignancy.htmhttp://www.moffitt.usf.edu/pubs/ccj/v5n2/article5.html (this is a related article. when I did my research I often looked outside the box of AN and looked at treatment options for brain tumors.
The only info that source provides on
radiosurgery is this:
High-intensity, focused radiotherapy (gamma knife or linear accelerator radiosurgery) is effective in reducing the growth rate of benign or intermediate malignant tumors.
The experience of radiation therapy, especially radiosurgery, has increased dramatically during the last decade, and the success rate of tumor control is high. In initial reports of radiosurgery on vestibular schwannomas, complications included cranial neuropathy consisting of 30% delayed facial paresis, 50% hearing loss, and 33% trigeminal neuropathy.25 Recently, the result has been revised with better outcomes achieved with a new dosimetry plan. However, it is not clear if a lower dose will result in the same rate of tumor control. Additionally, patients who have recurrent tumors after radiosurgery experience worse outcomes with microsurgery.10
The last part is disputed in the neurosurgeon community, but even if true, I'd take a 2-3% chance of a more difficult surgery, with the 97% chance to avoid surgery any day. But that's a personal choice that must be made.
The rest of the info pertains to
radiotherapy, which is not stereotactic and radiates healthy tissue as well. And even with radiotherapy, your source still gives a control rate of 97%, and cites the complication rate as minimal. Maybe you understood conventional fractionated radiotherapy to be the same as FSR, but it is different. If that's the case, Dr. Medberry's comment about imperfect understanding rings true.
What I had read was that since the AN and the nerve are made of the same cells they are equally susceptible to radiation and thus both can be damaged. Where as cancerous cells were often more radiosensitive than the surrounding cells and this often improved the efficacy of the treatment.
If radiation can damage an AN it can damage your facial nerve.
Actually, the AN is made of the same cells as the nerve
sheath, not the nerve itself. Schwann cells are the cells that surround the nerve. Nerve cells are called neurons. Nerve cells have a much better ability to recover than schwann cells, and that ability is thought to be even more when using hypofractionated radiosurgery, radiosurgery done over 3-5 sessions, not to be confused with conventional fractionated radiotherapy. And again, it doesn't work better on cancer cells, just faster, and mostly only on cancer cells that are metastatic, not primary brain cancer. If it were the case that radiation was more efficient on cancer cells, the GBM would be cured in days.
