S302 ESTRO 35 2016 ______________________________________________________________________________________________________ hippocampus dose was Dmax less than 17Gy without compromising the coverage of planning target volume (PTV) and other organs at risk were prioritized over hippocampal constraint. The mini-mental state examination (MMSE) and Seoul verbal learning test for total recall, delayed recall and recognition (SVLT-TR, DR, R) were performed at baseline and at 7 and 13 or 16 months after

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... radiotherapy. Results: A total of 41 patients were accrued. Median age was 48 years (range 26-76) and 51.2 % of the patients were male. Eighteen patients (43.9%) had WHO grade I or II tumor whereas 23 patients (56.1%) had grade III or IV tumor. Median volume of PTV was 192.8 cc (range 33.4-522.6) and median prescribed dose was 60Gy (range 46-66). Concurrent chemotherapy was given to 18 patients (43.9%). Median D100% and Dmax to the contralateral hippocampus were 7.7Gy (range 0.6-24.8) and 16.6 Gy (range 3.56-60.4) respectively. Mean dose to contralateral hippocampus could be spared to less than 21 Gy in 39 patients with median value of 11.6 Gy (range 0.3-37.3) which was lower compared to previous documentation. Median value of maximal dose to lenses and eyeballs were 4.3 Gy (0.4-8.1) and 13.7 Gy (0.5-46.6) respectively. At median follow up of 7.8 months (range 0-14.8), median progression-free survival and overall survival were not reached. Cognitive function tests at 7 months were analyzable in 12 patients. For these patients, MMSE, SVLT-TR, SVLT-DR and SVLT-R at 7 months showed improved results compared to the baseline with 2.0% (95% CI, -0.8% to 4.7%), 11.0% (95% CI, 3.3% to 18.8%), 20.1% (-5.5% to 45.8%) and -0.6% (95% CI, -6.6% to 8.2%) increase respectively. No grade 4 or 5 toxicity was reported. Conclusion: Hippocampus could be spared effectively in radiotherapy to primary brain tumors using VMAT. Despite limited follow up data, cognitive function tests of the patients showed promising results. Further follow up data would clarify the effect of hippocampal sparing on the cognitive function of the patients treated with radiotherapy for primary brain tumor.