From my readings, and I only read about SCCHN, mainly oropharyngeal, Oral Cancer, dosing above 30Gy will totally destroy the salivary glands, but could be wrong, and will not recover, as other vital structures have limiting toxicity dosing like the brain stem, spinal cord, brachial plexus nerve, so they don't get the full 70Gy. It depends if the salivary glands were involved with cancer, suspected, that would need higher dosage, but it's usually 26Gy to the salivary glands. It doesn't appear it's steady over the course of treatment, according to my colored "cumulative dose volume histogram" which has the dose, ratio of total structure volume (%), and relative dose (%), and have other colored copies of the CT, fields in plans in different positions. I can see my left, cancerous side, field was much larger. It's pretty cool if you can get copies.