Superficial Tumor Treatment with CyberKnife Device in the Head: An Alternative to Standard Radiation Therapy

Author(s): Anna Ianiro, Erminia Infusino*, Marco D’Andrea, Silvia Takanen, Laura Marucci, Francesco Quagliani, Jacopo Costantini, Antonella Soriani.

Purpose: The treatment of superficial head tumors with standard linear accelerators (linacs) often requires a bolus and/or multiple non-coplanar beams to increase surface dose and ensure adequate skin coverage. This study evaluates whether the CyberKnife (CK) system can serve as a valid alternative to these conventional methods. Methods: Fourteen patients with superficial tumor in the head were treated at our Institution with CK. All patients were retrospectively re-planned for linac treatment with bolus and in some cases with multiple no-coplanar beams. CK and linac plan quality was evaluated and compared through dose volume histogram (DVH) and dose distribution metrics. Plan deliverability was also verified through 2D gamma analysis. Results: For both techniques, all plans produced gamma pass rates above 90%. Target coverage resulted significantly higher for CK plans, while the volume of brain receiving 95% of prescription dose (V95, brain) was significantly lower. Dose distribution parameters analysis highlighted better conformity and gradient metrics in favor of CK plans, while no difference in homogeneity was noticed. Delivery time for CK plans resulted significantly higher with respect to VMAT plans. Regarding clinical outcome, of the 8 patients that showed at follow-up after 2 years, 7 had total response and 1 had partial response. Conclusions: CyberKnife is a valid alternative for treating superficial head tumors, offering superior dosimetry performance without the need for a bolus. Additionally, CK eliminates the need for couch movements required by non-coplanar linac techniques, improving treatment reproducibility and reducing setup uncertainties.