triplewave, if you're after hearign preservation, observation has the best outcome. From this paper ( https://pdfs.semanticscholar.org/2cef/abe8e8eef1ae32cab8bcf3c71dd75f53387c.pdf
), Gamma Knife accelerates hearing loss and watch and wait gives the best outcomes with regards to hearing. Notably:"In the literature, to our knowledge, there have been no reports of the hearing preservation after 10 years or more after hearing preservation surgery or radiotherapy. In the present study [no active treatment], 95 patients had been observed for 10 years or more. According to the AAO classification, 46% maintained good hearing after 10 years or more compared with 45% using the WRS classification and 75% of patients with 100% speech discrimination at diagnosis.".
I don't know how your neurosurgeon puts the risk of permanent facial nerve damage at a low 1%. I was given the figure (for a slightly larger tumor) of 30% risk of damage. The paper http://bmjopen.bmj.com/content/bmjopen/3/2/e001345.full.pdf
has the risk of facial nerve neuropathy at 10 to 30%, depending on size. And reports in papers are usually from the best centers with the best outcomes reported. Surgeons, as most people, overestimate their abilities, but 1% sounds off the scale. (Also, like most things, there is a scale. The House Brackmann scale defines facial nerve function from HB1 (perfect) to HB VI (total paralysis). Anything below HB III is quality of life affecting.)
Long term radiation effects are not known. If they were, more definitive options would be conveyed.
Radiotherapy normally targets 12 Gray at the 50% isodose level. That means that areas closer to the center get more radiation, the border gets 12 Gray and it drops off from there. For instance, you want to target a cochlear dose less than 4 Gray. Flying from coast-to-coast is 0.0003 Gray (and fractionated :-) ). If my calculating are correct, radiotherapy has a marginal dose thats about 3500 times greater than a CT, which in turn is about 500 times more than an x-ray.
My unprofessional opinion is that radiotherapy radiation doses are much more than from a CT, which is much more than from an x-ray, which is much more than naturally occurring. Keep in mind that one large dose is not the same as many small even if the radiatino dose is the same.
With regard to radiation the tumor and the collateral damage on the cochlear nerve and facial nerve, the facial nerve appears to be hardier. The cochlear nerve get more damage, but this can take years to show symptoms. After 10 years, it's very rare to still have useful hearing.
With regards to tumor growth there's only one way to find out - and that's a series of follow up MRIs. In the literature, age, tumor size and sex have no correlation with growth. The only prognostic factor is growth in the first year. Also, tumors grow more slowly with time (Table 1 from http://acusticusneurinom.dk/wp-content/uploads/2015/10/natural-history-of-vs.pdf
) and don't grow after 4 years from diagnosis. So unless you have rapid growth, or sustained significant growth, you've achieved what radiotherapy attempts to achieve.
Read the paper summaries in the reference section of https://www.bhtinformatie.nl/pdf/ingrijpen.pdf