Some Comments on Malignancy, Gamma Knife and Radiotherapy..
Many of us are a little scared of the thoughts of malignancy.
I think we need to put the risk into perspective.
First of all many of us would have had a had CT-Scan or two and thought absolutely nothing of it.
The risk of getting Cancer from your CT-Scan is relatively high, possibly as high as 1:400,
The risk isn't even declared.
https://www.ncbi.nlm.nih.gov/pubmed/20008690 An Excerpt From Scientific American
"A handful of studies published in the past decade have rekindled concerns. Researchers at the National Cancer Institute estimate that 29,000 future cancer cases could be attributed to the 72 million CT scans performed in the country in 2007. That increase is equivalent to about 2 percent of the total 1.7 million cancers diagnosed nationwide every year. A 2009 study of medical centers in the San Francisco Bay Area also calculated an elevated risk: one extra case of cancer for every 400 to 2,000 routine chest CT exams."
On Radiosurgery.
Some people are naturally susceptible to radiation and it is theorised more likely to have a malignant transformation.
People with NF2 have a genetic defect that makes them more susceptible to tumours.
No surprise then that many of the noted malignant transformations are associated with NF-2
https://www.ncbi.nlm.nih.gov/pubmed/17460521It could very well be that Radiosurgery is very safe for 98% of the population, but far more risky to people that have a predisposition to cancer, and lack tumour suppression mechanisms.
Other factors as ASG has noted is the dosage of the treatment.
AN's receive a relatively low dose, which reduces the risk...
Different tumour types may also indicate that you have a predisposition for cancer.
There is an interesting paper here demonstrating a link between AN treatment failure and an Unrelated Malignancy.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3379795/A paper indicating FSRT increases the risk of Malignancy.... Why get 48Gy when you can get 12-13Gy
https://www.ncbi.nlm.nih.gov/pubmed/15179297"Many publications emphaze the risks after larger-field, fractionated radiotherapy with low non-cell-killing dose delivered to central nervous system. Furthermore, therapeutic radiation doses for benign tumors associated with a long life (parasellar tumors, meningioma) were implicated in carcinogenesis. Incidence of radiation-associated tumors is linked to different factors such as age and individual genetic susceptibility."
Another factor is Tumour volume.
It takes about 100 times the radiation to zap a 3.0cm tumour versus a 10mm tumour.
By volume a 3cm tumour is nearly 100 times larger. Presumably receiving 100 times the radiation increases your risk 100 fold.
Even if you do have a malignant transformation of an AN, I believe about 75% had the cancer removed successfully.
You also need to balance that out with the risks of surgery.
Mortality rates in the US are averaging 0.5% and 6% requiring rehabilitation.
Choosing an experienced Doc reduces your risks by 70%. probably more for the best teams.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3199160/