Chances of malignant transformation following radiosurgery

[ANSydney]

It appears that the big decider about whether to opt for microsurgery or radiosurgery is the chance of a malignant transformation. I've always matched the chance of death from a microsurgery (about 0.5%) to the chance of a malignant transformation from radiosurgery (I thought it was small, but ...)

Articles such as https://www.ncbi.nlm.nih.gov/pubmed/25434949 tell me the chance of a malignant transformation is 0.016% over 20 years, which is a better figure that death from microsurgery. This made radiosurgery appear as the better option since in every other outcome it is better.

Things have been turned upside down since an article was published ahead of print on 9 January 2017 (just 6 days ago). http://www.sciencedirect.com/science/article/pii/S0360301617300044 has the chance of a malignant transformation at 2.4% over 15 years. Actually less for vestibular schwannoma since other tumors such as meningioma were considered. Excluding these brings it lower to something like 0.5%

Which is right? Is the risk negligible (0.016%) or about 0.5%?

(BTW, it took me some time to realize that the second article was talking about both "radiation-induced tumors" (a new tumor) or "malignant transformation" (existing benign tumor turning malignant).

[Willbur]

Interesting find. You know Joe Biden's son had brain cancer and I always wondered if he had an acoustic neuroma that turned malignant, but that info isn't publicly available.

[theshawn65]

I would be interested to know if the numbers are GK or CK alone or are FSR treatments included.

Be that as it may, both Dr., the radiologist and the neurosurgeon implied the risk was statistically insignificant. Which I believe these studies bear out.

[Echo]

From all the research that I did prior to having GK, and conversations I had with neurosurgeons, any malignant growth was such a remote possibility that it didn't really factor into how I made my decision.  My biggest concern was maintaining quality of life, given all the possible outcomes from microsurgery.  As a single person in my late 50's, I wanted and needed to continue working.  I also had an elderly parent to care for.  I had a previous bad experience with anesthetic on a 2 hour surgery so facing a substantially longer AN surgery wasn't high on my list of things to look forward to.  GK, allowed me to return to work quickly while continuing to care for my mom. Facial paralysis was a non issue and while my recovery wasn't a total walk in the park for the first 1 1/2 years, I was able to maintain a quality of life that was manageable and one I was happy with. 

We all need to weigh the issues that are important to us when making the decision on when to treat and what treatment we prefer. It's a challenging decision and definitely the toughest one I've ever made.

Cathie

[PaulW]

There are many factors which vary the chance of malignant transformation.
The more radiation you receive the greater the chance of malignant transformation.
The amount of radiation you receive is related to the volume of your tumour.
My AN was 10x5x5mm and the tumour volume was 0.15cm3... Which is nearly 100 times smaller by volume than a 3cm tumour. So tumour volume is a huge factor.
It should also be noted that different machines will spread more or less radiation too.
So equipment choice will also affect the risk.

Next factor is your genetic propensity for cancer.
People with NF2 I believe are about 10 times more likely to have a. Malignant transformation after radiation. People with meningiomas are also more susceptible to cancer and malignant transformation overall.

Radiation dosage.
AN's are typically treated with 12-13Gy other tumours can be treated with much higher doses.
Meningiomas are more aggressive and are often treated with higher dosages

Surface area of the tumour.
Meningiomas often have a large surface area, they are often wide and thin. Acoustic neuromas are normally a ball. Many malignant transformations happen at the tumour bed, an area that probably received the full dose of radiation especially with older equipment, a 2mm safety margin would equate to 2mm of brain getting zapped with the same dose as the tumour. So a lot more good stuff gets zapped with a big surface area.

There are also recorded cases of malignant transformation after surgery for acoustic neuromas.

If you remove NF-2 and the number of people that have malignant transformation from surgery from the numbers the chances are low.