I just found this on an FAQ for PBT
http://www.proton-therapy.org/questions.htm

Can proton therapy be used in conjunction with other forms of cancer treatment?

Yes. Depending on the case, proton therapy may be used in combination with traditional radiation, chemotherapy and/or as a follow-up to surgery.

My doctor never mentioned proton therapy as a cancer treatment option? How long has proton therapy been in use for medical purposes?

Proton Therapy was first proposed in 1954, but primarily had been available for very limited use. There was no hospital-based treatment centers in the world until the Proton Treatment Center opened in 1990 at Loma Linda University Medical Center. Most radiation oncologists know about proton therapy, but have not had experience working with the proton technology, making it difficult for them to advise patients on this form of treatment.