Improving precision in Stereotactic Body Radiotherapy for oligometastatic disease.

In the last decade, Stereotactic Body Radiotherapy (SBRT) is being increasingly used for the treatment of oligometastatic disease. Two previous trials in our center demonstrated a high survival and a low toxicity, but the local control was deemed suboptimal. The first part of this thesis therefore describes a study to uncover the root cause of this issue, by analyzing the recurrences in comparison with the irradiated volume. The gained knowledge was used in a new prospective trial, with an emphasis on individual motion management. The introduction of the Vero SBRT system in our center allowed the implementation of dynamic tracking for lesions exhibiting large motion on 4D-CT imaging. Other lesions were treated with a motion-encompassing approach. This strategy was combined with a moderate dose escalation. The trial resulted in an adequate local control, offering a sensible treatment schedule, also suitable for lesions in close proximity to serial structures. In the final part we investigated the factors that differentiate oligometastatic patients with varying prognoses. Five independent adverse factors were discriminated. A nomogram enables estimation of survival and corresponding risk groups were determined. These patient groups with distinctive prognoses can be taken into account when treatment strategies are defined in clinical guidelines or prospective trials.

Publication year:2019

Keywords:Stereotactic Body Radiotherapy