Here is a new article about the effectiveness of carbon ion radiotherapy for localized primary sarcomas of the extremities:
http://www.ncbi.nlm.nih.gov/pubmed/23068710
According to wikipedia, only 2 facilities offered this technology in 2008 and they were both in Japan:
http://en.wikipedia.org/wiki/Particle_therapy#Carbon_ion_centers_in_operation
According to the following website, there are now 5 facilities but they don't specify where:
http://www.bestcyclotron.com/particletherapy/
Here is an article that talks about the history behind the technology: