Zemskova O. Radiosurgical treatment of vestibular schwannomasand neuroimaging evaluation of its efficacy

This study is dedicated to actual scientific problem of improvement results of radiosurgical treatment and neuroimaging monitoring of vestibular schwannomas. We analyzed the results of radiosurgical treatment of 143 patients with 145 vestibular schwannomas (VS) and data of the post-radiation neuroimaging monitoring. The evaluation of tumor growth control ratio was optimized by invention of new index - ratio of local control without the risk of tumor progression, that allows to consider the risk of possible further progression of relatively stable tumours. The patterns of changes of local control index ratio were determined in different follow-up periods after radiosurgical treatment of vestibular schwannomas. Statistically significant difference(p<0,05) in local control ratio was detected during first 24 months of follow-up and was absent after 36 months (max follow-up time 55 months). Hence, tumor response was seen in first 2 years of follow-up. It was proved, that invention of original method of radiosurgical treatment DynArc + IMRTsignificantly increased its efficacy (p=0,022). The feasability of neuroimaging data application and dose regimen as predictors of response to radiosurgical treatment in patients with VS was also proved. New predictors of local control were investigated.It was established, that data of perfusion CT (gap(MTT) х gap(CBV)) are the strongest predictive factor influencing median tumor growth control ratio. New mathematical model of response prognosis of VS on radiosurgical treatment was carried out.It allows to calculate the optimal time periods for postradiational neuroimaging monitoring during which decreases the frequency of imaging procedures during follow-up.