Abstract: ObjectiveTo study the effect and feasibility of simultaneous integrated boostintensity modulated         radiotherapy (SIBIMRT) for metastatic malignancies palliative care patients with metastatic malignant cancer. MethodsFortyfive patients with metastatic malignant cancer were treated with SIBIMRT for 10 to 28 fractions. The gross target volume (GTV) was 2.05.0 Gy per fraction, and the marginal dose of the planning target volume (PTV) was 1.83.0 Gy per fraction. For comparing the different delivering techniques, the three dimensionalconformal radiotherapy (3DCRT) plan for each patient was optimized. The effects and adverse effects were evaluated in the first month′s followup and every three months thereafter. ResultsAll patients completed the radiation therapy except for one who developed severe hepatic abscess. Nineteen patients received concurrent intravenous or oral chemotherapy or targeted drug therapies. The proportion of patients without adverse reaction was 38.64%（17/44）, and the incidence rate of grade ⅠⅡ digestive tract or bone marrow suppression was 56.82% (25/44). Only 3 patients (6.82%) occurred grade Ⅲ bone marrow suppression, and no grade Ⅲ gastrointestinal reaction and Ⅳ adverse reaction occurred. The mean doses of GTV were (5 556.1±925.6) cGy for SIBIMRT and (4 491.5±881.4) cGy for 3DCRT, with 23.7% increase (t=15.492, P=0.00). One hundred and sixtyseven organs at risk (OARs) including lungs, intestine, spine, kidneys and liver were evaluated. Seventytwo OARs had decreased irradiation dose with SIBIMRT compared with 3DCRT, the range of the decrease ratio was 0.50%77.43%, with a mean value of 19.71%. Ninetyfive OARs had elevated irradiation dose with SIBIMRT compared with 3DCRT, the range of the increase ratio was 0.59%86.71%, with a mean value of 18.13%. The total mean value was increased 0.86%. So the SIBIMRT was acceptable. The median followup duration was 10 months （526 months）. Two patients dropped out. The relapsefree rate within the radiation field was 95.23% (40/42). ConclusionSIBIMRT can significantly increase radiation doses of the tumor fields. The doses of OARs with SIBIMRT are increased or some decreased, and the range of the increased dose is indistinctive, and the patients are well tolerated.

Key words: Neoplasms, Radiotherapy, Palliative care