Use of simultaneous radiation boost achieves high treatment response rate in patients with metastatic gastric cancer.

Objective: Intensity-modulated radiation therapy (IMRT) with a simultaneous integrated boost (SIB) could improve local control rates at different anatomic sites. However, little is known for its use in metastatic gastric cancer. Our study aimed to compare the treatment response rates of IMRI-SIB and conformal radiotherapy (CRT) in patients with metastatic gastric cancer. Materials and Methods: We retrospectively identified twenty patients with metastatic gastric cancer from 2013 to 2015, 12 given IMRT-SIB, and eight given CRT. Treatment response and toxicities were evaluated for all patients. The radiation target included peritoneal lymph nodes. RECIST criteria were used to assess the treatment response. Three patients of eight in the CRT group died before the end of treatment due to the progression of diseases in the field. Results: For the IMRT-SIB group, the median dose of high dose field was 60.8 Gy (50-64.4 Gy), and the median dose of low-dose field was 45 Gy (36-50.4 Gy). For the CRT group, the median dose of the total dose was 50 Gy (41.4-60 Gy). IMRT-SIB could elevate local dose significantly, compared to the CRT group. One patient of 12 in the IMRT-SIB group achieved complete response, and nine patients achieved partial response (PR), whereas no patient achieved CR in the CRT group. Two of five patients achieved PR (40%) in the CRT group. IMRT-SIB improved the treatment response rate significantly (odds ratio 8.33, 95% confidence interval: 1.03-67.14, P = 0.046). Two patients of 12 in the IMRT-SIB group developed enteritis, whereas two patients of five developed enteritis in the CRT group. Conclusions: IMRT-SIB could escalate the local dose and improve the treatment response rates in patients with metastatic gastric cancer and with acceptable toxicities. Further study with a larger population to validate our data is underway.