MET-05 Clinical investigation of treatment results and recurrence patterns of metastatic brain tumors from the viewpoint of postoperative irradiation

While whole brain radiation therapy (WBRT) had been the standard postoperative radiation therapy for metastatic brain tumors for long time, recently local radiation therapy (LRT) has be become to be a new standard due to the accumulation of clinical evidences. Treatment results and pattern of recurrence were retrospectively analyzed from view point of postoperative radiotherapy. In this study, totally 69 patients were included and they were divided into WBRT group or LRT group. We analyzed the number of lesions, treated era, overall survival after diagnosis of metastasis (OS), recurrence free survival after RT (RFS), and patterns of recurrences. The subjects consisted of 37males and 32 females and average age was 61.7 years old. There were 49 cases in the WBRT group and 20 cases in the LRT group. While all cases before November 2017 had WBRT performed, LRT was adopted mainly in cases with a small number of metastases since December 2017. Although there was a difference in the observation period between the two groups, OS tended to be longer in the LRT group (P=0.08), while RFS tended to be shorter in the LRT group (P=0.08). Radiological recurrence after RT was observed in 7 cases in both groups, and in WBRT group, all cases were local recurrence, whereas in LRT group, all cases were new lesions or disseminated recurrence. Although there are biases such as the difference in observation period between the two groups and the tendency to adopt WBRT in cases with a large number of metastases, there is a possibility that postoperative LRT is not inferior to WBRT, especially for cases with a small number of metastases. However, we have experienced some cases of disseminated recurrence, and so it is necessary to consider the resection fashion such as whether en-bloc resection or piece meal resection when selecting postoperative RT.