[1] Univ Maryland, Med Ctr, Dept Radiat Oncol, Baltimore, MD 21201 USA
[2] Univ Maryland, Sch Med, Baltimore, MD 21201 USA
[3] Univ Maryland, Greenebaum Canc Ctr, Div Biostat & Bioinformat, Baltimore, MD 21201 USA
[4] Univ Maryland, Sch Med, Dept Epidemiol & Publ Hlth, Baltimore, MD 21201 USA
[5] Univ Maryland, Sch Med, Dept Radiat Oncol, Baltimore, MD 21201 USA
[6] Univ Maryland, Proton Treatment Ctr, Dept Radiat Oncol, Baltimore, MD 21201 USA
[7] Maryland Proton Treatment Ctr, Baltimore, MD USA