Purpose: The aim of this work is to report a retrospective study of radiobiological indicators based on Dose-Volume Histograms analysis obtained by stereotactic radiotherapy treatments.
Methods and materials: Fifty-five patients for a total of sixty-seven brain metastases with a mean target volume of 8.49 cc were treated by Dynamic Conformal Arc Therapy (DCAT) and Intensity-Modulated Stereotactic Radiotherapy (IMRST). The Delivered prescription dose was chosen on the basis of tumor size and location so as to ensure a 100% isodose coverage to the target volume.
Results: The treatment plans reported a mean value of 10% and 2.19% for the inhomogeneity and conformal index, respectively. The F factor showed we overdosed sixty-three patients delivering an additional 7% dose more than calculated values. The radiobiological parameters: TCP and NTCP showed a complete tumor control limiting the organs at risk damage.
Conclusion: One goal of stereotactic radiotherapy is to design a treatment plan in which the steep dose gradient achievable minimizes the amount of radiation delivered outside the tumor region. This technique allows to deliver a much larger dose to the target without exceeding the radiation-related tolerance of normal tissues and improving patients' quality of life.