SAFESTEREO: phase II randomized trial to compare stereotactic radiosurgery with fractionated stereotactic radiosurgery for brain metastases.

BACKGROUND: Stereotactic radiosurgery (SRS) is a frequently chosen treatment for patients with brain metastases and the number of long-term survivors is increasing. Brain necrosis (e.g. radionecrosis) is the most important long-term side effect of the treatment. Retrospective studies show a lower risk of radionecrosis and local tumor recurrence after fractionated stereotactic radiosurgery (fSRS, e.g. five fractions) compared with stereotactic radiosurgery in one or three fractions. This is especially true for patients with large brain metastases. As such, the 2022 ASTRO guideline of radiotherapy for brain metastases recommends more research to fSRS to reduce the risk of radionecrosis. This multicenter prospective randomized study aims to determine whether the incidence of adverse local events (either local failure or radionecrosis) can be reduced using fSRS versus SRS in one or three fractions in patients with brain metastases. METHODS: Patients are eligible with one or more brain metastases from a solid primary tumor, age of 18 years or older, and a Karnofsky Performance Status ≥ 70. Exclusion criteria include patients with small cell lung cancer, germinoma or lymphoma, leptomeningeal metastases, a contraindication for MRI, prior inclusion in this study, prior surgery for brain metastases, prior radiotherapy for the same brain metastases (in-field re-irradiation). Participants will be randomized between SRS with a dose of 15-24 Gy in 1 or 3 fractions (standard arm) or fSRS 35 Gy in five fractions (experimental arm). The primary endpoint is the incidence of a local adverse event (local tumor failure or radionecrosis identified on MRI scans) at two years after treatment. Secondary endpoints are salvage treatment and the use of corticosteroids, bevacizumab, or antiepileptic drugs, survival, distant brain recurrences, toxicity, and quality of life. DISCUSSION: Currently, limiting the risk of adverse events such as radionecrosis is a major challenge in the treatment of brain metastases. fSRS potentially reduces this risk of radionecrosis and local tumor failure. TRIAL REGISTRATION: ClincalTrials.gov, trial registration number: NCT05346367 , trial registration date: 26 April 2022.

Optimal image guided radiation therapy strategy for organs at risk sparing in radiotherapy of the prostate including pelvic lymph nodes.

BACKGROUND AND PURPOSE: Purpose of this study was to quantify the OAR dose for different position correction strategies, and to determine which strategy is most optimal for treating patients on the prostate and pelvic lymph nodes. MATERIALS AND METHODS: For 30 patients, four different treatment plans were made reflecting different correction strategies: online correction on bony anatomy; offline correction on bony anatomy; online correction on the prostate fiducials; using 1 cm margins around both CTVs. The dose to the PTVs and OARs was quantified and a pairwise statistical analysis was performed. RESULTS: No statistically significant differences were observed in the dose to the PTVs, ensuring that any OAR sparing is not caused by differences in PTV coverage. Dose to the rectum and anal canal was lowest when applying an online correction on prostate fiducials, although the total PTV volume was higher. Dose to the small bowel bag and femoral heads was slightly higher compared to online correction on bony structures, but well within clinically acceptable limits. CONCLUSION: Although the total PTV volume is higher when applying an online correction on the prostate, this strategy leads to the most optimal sparing of relevant OARs, at the cost of a slightly higher dose to the femoral heads and small bowel bag.