Session Item

Stereotactic radiosurgery (SRS) is an increasingly utilized and well tolerated treatment for benign skull base tumors such as glomus jugulare and acoustic schwannoma. Treatment planning of those tumors is particularly complex because of the close proximity of the critical structures.CyberKnife (CK) is a SRS technique that ensures highly conformal dose distrubutions using a linac based robotic arm and image guidance with real-time tumor tracking. We retrospectively  aimed  to evaluate  the  clinical  feasibility  and dosimetric outcomes of the target and the normal tissues with MLC and fixed cone-based plans in benign skull base tumors.

Eleven acoustic schwannoma and 7 glomus jugulare patients were treated with CK-M6 and the plans with different collimators were retrospectively evaluated. Parameters such as treatment time, homogenity index (HI), conformity index (CI) and gradient index (GI), monitor units (MUs)  and volumetric doses of brain,  brainstem, cochlea, were analyzed. The obtained  dosimetric outcomes were compared to each other to define the best treatment technique.

In our analysis, cochlea dose was significantly lower in MLC plans compared to fixed ones (p:0,023).  Brainstem maximum point dose and also V10 Gy and V15 Gy of brain were significantly lower in  MLC plans (p:0,021, p:0,014, p:0,000, retrospectively). Due to MLC plans consist of less nodes and  segments in comparison to fixed plans, use less MU and are deliverable in a shorter treatment time (p: 0,00). The average delivered MUs in MLC plans are lower by 45 % (p:0,000).

We obtained the feasibility of shorter time delivery efficiency and reduced delivered MU with  MLC plans.  Each plans were equivalant regarding tumor coverage and dose distrubution. MLC plans provided preferable protection on critical structures and consistently showed better dose gradient fall of in our study