Michelle, It's interesting you think there's a family history because my understanding is that with this cancer, there doesn't seem to be much relationship to genetics, but maybe there is and it just hasn't been found yet.

I can try to explain perineural invasion (because I had a small, barely Stage II in size, tumor which had it). My understanding is it is when the tumor is growing along or around a nerve. Cancer can spread through lymph fluid, the blood and (less commonly)via the nervous system so perineural invasion basically means there is another pathway by which cancer cells *may* have migrated elsewhere from the tumor which was removed. There has been some research showing it to be a significant risk factor for recurrence.

I had perineural invasion and had IMRT (and was told in my second opinion at a leading cancer center that IMRT would be a fine way to treat me, even with the perineural invasion), but for what it's worth (and I'm not a doctor just someone who's done some reading on this), I can see why someone might think conventional rad would be better with perineural invasion because in your mother's case, as in mine, the tumor is already gone so where they are targeting the radiation using IMRT would be the primary tumor bed and the known pathways by which the cancer would spread--and that means primarily lymphatic pathways I think--my impression is not enough is known about how cancer would spread along nerves to target neural pathways. But, again, I'm not a doctor and I could be wrong about this.

Anyway, I hope this helps.

Nelie