Comparison of advanced irradiation techniques with photons for benign intracranial tumours

The potential benefits and limitations of different radiation techniques (stereotactic arc therapy (SRS/T), intensity modulated radiotherapy (IMRT), helical tomotherapy (HT), Cyberknife and intensity-modulated multiple arc therapy (AMOA)) have been assessed using comparative treatment planning methods on twelve patients presenting with 'benign' brain tumours.

Plans for five acoustic neurinomas, five meningiomas and two pituitary adenomas were computed to generate dose distributions for all modalities using a common CT dataset to delineate planning target volume and organs at risk.

HT, AMOA and IMRT resulted superior to SRS/T and Cyberknife for target coverage. For the first group V(95%) ranged from 98% to 100%, minimum dose ranged from 91% to 96% and standard deviation from 0.84% to 1.67%. For organs at risk all techniques respected planning objectives with a tendency of Cyberknife and SRS/T to better spare the brain stem and the healthy brain tissue (e.g., V(20Gy) of 2.0% and 2.3%, respectively, compared to 3.1-5.0% for the other techniques). AMOA is in general preferable to IMRT for all OARs. Conformity index (CI(95)) was better for HT and Cyberknife (both 1.8) and less for AMOA and IMRT (3.9 and 3.0, respectively).

All techniques provided good OAR sparing and primarily differed in target coverage indices. For the class of tumours investigated in this report, HT, AMOA and IMRT had better target coverage with HT providing the best combination of indeces. Between AMOA and IMRT, target coverage was comparable and, considering organs at risk, AMOA was slightly preferable.