| Karmanos Cancer Institute | Christian Hyde | PI |
| Northwestern University | Arpi Thukral, MD | PI - enrolling physician |
| Inova | Ashish Chawla, MD | PI - enrolling physician |
| Thompson Proton Center (formerly Provison) | Ben Wilkinson, MD | PI - enrolling physician |
| Rutgers Cancer Institue of New Jersey | Bruce Haffty, MD | PI - enrolling physician |
| University of Miami Cancer Center | Cristiane Takita, MD | PI - enrolling physician |
| UPMC Pinnacle | David Weksberg, MD, PhD | PI - enrolling physician |
| University of Pennsylvania | Gary Freedman, MD | PI - enrolling physician |
| University of Alabama-Birmingham | Hunter Boggs, MD | PI - enrolling physician |
| Washington University in St. Louis | Imran Zoberi, MD/Walter Bosch, DSc | PI - enrolling physician |
| NY Proton Center | J. Isabel Choi, MD | PI - enrolling physician |
| University of California San Diego | James Urbanic | PI - enrolling physician |
| University of Washington | Janice Kim, MD | PI - enrolling physician |
| UH Case Western | Janice Lyons, MD | PI - enrolling physician |
| Texas Center for Proton Therapy | Jared Sturgeon, MD | PI - enrolling physician |
| Johns Hopkins University | Jean Wright, MD | PI - enrolling physician |
| University of Florida | Julie Bradley, MD | PI - enrolling physician |
| UT MD Anderson Cancer Center | Karen Hoffman, MD | PI - enrolling physician |
| Memorial Sloan Kettering Cancer Center | Lior Z. Braunstein, MD | PI - enrolling physician |
| Mayo Clinic Arizona | Lisa McGee | PI - enrolling physician |
| Miami Cancer Center at Baptist Health | Marcio Fagundes | PI - enrolling physician |
| University of Maryland | Mark V. Mishra, MD | PI - enrolling physician |
| University of Oklahoma | Ozer Algan, MD | PI - enrolling physician |
| Mayo Clinic Rochester | Robert W. Mutter | PI - enrolling physician |
| Emory University | Sagar Patel, MD | PI - enrolling physician |
| Massachusetts General Hospital | Shannon M. MacDonald, MD | PI - enrolling physician |
| Georgetown University | Sonali Rudra, MD | PI - enrolling physician |
| University of Cincinnati | Teresa Meier, MD | PI - enrolling physician |
| Orlando Health | Tomas Dvorak | PI - enrolling physician |
| Radiation Therapy Oncology Group | Stephanie Pugh, PhD | Statistician |
