ESTRO 2021 Abstract Book

S1184

ESTRO 2021

Median follow-up time was 19.4 months (95% CI, 17.7–24.3). We observed nine local progressions after SRS and the 3-month, 6-month, 12-months, and 18-month local control rates were 97.4%, 86%, 69.2%, and 52.6%, respectively. The median Local PFS was 10.3 months (95% CI 7.2–14.3). WBRT did not influence these results. Figure 1 shows the time to to local progression.

Sixty (61.2%) brain progression occurred outside of treated lesions. The 3-, 6-, 12-, and 18-months brain control were 81.5%, 52.4%, 24%, and 14.5%, respectively. In multivariate analysis, more than one irradiated brain metastases was associated with an increased risk of brain progression (HR 1.81, 95% CI 1.16–2.83, p = 0.0094). Median OS time was 12.2 months (95% CI 8.2–14.4). KPS was the only prognostic factor for overall survival on multivariate analysis (HR 0.96 95% CI 0.94–0.98 p <0.0001). Nine patients (9.3%) experienced a Grade 2 acute brain toxicity requiring an increase dose of corticosteroids. Twenty lesions showed signs of radionecrosis (18.9%), and 8/20 were symptomatic (e.g. neurological symptoms worsening, intracranial hypertension). WBRT did not increase the risk of radionecrosis ( p =0.72). None of the dosimetric and clinical parameters that were tested showed any significant influence on the risk of radionecrosis. Figure 2 shows the incidence of radionecrosis in the followup.