A retrospective study by MSKCC etc multi-centers. 26 patients with recurrent or metastatic cancers were treated with palliative proton RT to the head and neck with quad shot (3.7 Gy twice daily for 2 days). Seventeen (65%) patients received ≥ 3 quad-shot cycles and 23 (88%) had prior head and neck RT.

Overall palliative response was 73% (n = 19). The most common presenting symptom was pain (50%; n = 13), which improved in 85% (n = 22) of all patients. The overall grade-1 acute-toxicity rate was 58% (n = 15), and no acute grade 3 to 5 toxicities were observed. The authors concluded that proton quad-shot regimen demonstrates favorable palliative response and toxicity profile.