Abstract: Background and purpose: The incidence of lung cancer with brain metastasis tends to go up. The technique of intensity-modulated radiotherapy (IMRT) with simultaneous integrated boost (SIB) for tumor bed is a new treatment choice for patients with brain metastasis. This study aimed to investigate the feasibility of IMRT combined with SIB for tumor bed in the treatment of brain metastases of lung cancer by exploring its short-term clinical effect and treatment-related toxicities. Methods: Thirty-two patients who were diagnosed as having lung cancer with 1-4 brain metastases were prospectively collected. All the brain metastases were treated with whole brain 5 fields IMRT (40 Gy/20 f) combined with SIB (50 Gy/20 f). The dosage distribution within the target volume and dose-volume histogram were evaluated. Meanwhile, the overall response rate of radiotherapy, the local tumor control rate, 1-year survival rate, treatment-related acute and late toxicities were also calculated. Results: All patients were treated with IMRT successfully. The rate of Grade 2 vomitting, nausea, epilepsy was 9.4%, 15.6%, and 12.5%, respectively. Two cases had Grade 2 cognitive impairment, 4 cases had Grade 2 memory injury, and 2 cases had Grade 3 memory injury. There were no any Grade 4 events of acute and late toxicities. The overall response rate of radiotherapy was 71.9%. The local tumor control rate was 96.9%, and 1-year survival rate was 44%. Conclusion: It is feasible to use 5 fields IMRT (40 Gy/20 f) combined with SIB (boosting 10 Gy, i.e. total dose 50 Gy/20 f) for the treatment of brain metastases of lung cancer.

Key words: Intensity-modulated radiotherapy, Lung cancer, Brain metastasis, Simultaneous integrated boost