MNG-08 VOLUMETRIC STUDIES IN ASYMPTOMATIC MENINGIOMAS: SLOWDOWN CASES AND GROWTH ARREST CASES

BACKGROUND: The opportunity to follow up for asymptomatic meningiomas has increased. We have reported the risk of volume increase by individual continuous volume measurement of asymptomatic meningiomas. However, We have not reached fully understanding about natural history of meningiomas. Among cases are followed up over time, there are some cases that the volume increase rates slows down or almost stops are observed. METHODS: We enrolled consecutive adult patients of asymptomatic meningiomas who follow-up for 2 years or more and 3 or more MRI scans. We performed sequential volumetric measurements on 95 patients (105 lesions) who met the criteria. We classified these transient volume curve of each lesion into three groups “Growing”, “Slowdown”, and “Growth arrest” for analysis. RESULTS: The average age at the first visit was 62.8 years, the average follow-up period was 61.8 months, and the male-female ratio was 20:75 (male: female). There were 67 cases (73 lesions: 70.9%) that were in increasing trend, and 19 cases of those were received resection. Eleven cases (12 lesions: 11.7%) showed a tendency of “slow down” the increase rate, and one patient who became symptomatic led to surgical excision. In 18 cases (18 lesions: 17.4%) in which almost no volume change was observed during the observation period, no cases resulted in surgical treatment. CONCLUSIONS: Among the meningiomas cases that have been followed for a long time, there are not a few those increase rate of tumor volume slows or does not change. Furthermore, most of these cases did not result in surgical treatment. The presence of these “Slowdown” and “Growth arrest” cases at a certain rate may have suggested the possibility of a Gompertz curve model as the natural course of meningiomas.