We seem to rarely (if ever) see a post related to Neutron Therapy, but apparently the the side-effects are similar to IMRT.

According to this article, doctors use neutron therapy to treat only about 100 people a year with. About 80 percent of these patients have tumors of their major or minor salivary glands - There are only a few treatment facilities, one being U of W.

http://www.radonc.washington.edu/clinical-cyclotron/neutron-therapy/