ESTRO 2023 - Abstract Book

S897

Digital Posters

ESTRO 2023

To investigate the impact of adjuvant stereotactic radiotherapy (SRT) to the surgical cavity of resected brain metastases and compare clinical outcomes between patients receiving different postoperative strategies. Materials and Methods We retrospectively analyzed 120 patients referred to our institution between 2010 and 2020 after surgery for previously untreated brain metastases: 60 received adjuvant SRT to the resection cavity and 60 received alternative postoperative approaches (22 adjuvant whole brain RT, 9 adjuvant whole brain RT + simultaneous integrated boost to the surgical cavity, 29 observation). The primary endpoint was local control (LC) for the group treated with adjuvant SRT. Secondary endpoints were distant intracranial control (DIC), overall survival (OS), incidence of radionecrosis (RN) and incidence of leptomeningeal dissemination (LMD) after adjuvant SRT. Finally, we made an exploratory comparison in terms of LC, DIC and OS between all the different postoperative strategies. LC, DIC and OS were estimated using the Kaplan-Meier method. Chi-squared test was used to examine between-group covariate differences, and the Cox proportional hazards model was used for univariate and multivariate analyses to assess the effects of variables on clinical outcomes. Results With a median follow-up of 22 months (range 5-117 months), 1- and 2-year LC rates were 82% and 75% respectively for patients treated with adjuvant SRT. For these patients, primary tumor of lung and breast cancer or melanoma (p = 0.021) and Planning Target Volume (PTV) of the surgical cavity less than 13 cc (p = 0.026) were found to be significantly correlated with a better LC (Figure 1), while having received any type of concomitant systemic therapy had a marginal impact on LC (p = 0.062). DIC was 57% at 1 year and 48% at 2 years after adjuvant SRT. Median OS was 27 months, with 1- and 2-year rates of 72% and 50% respectively for patients treated with adjuvant SRT. RN occurred in 7 patients (11.7%), with a median interval of 13 months from the end of SRT, while LMD involved 4 patients (6.7%), with a median time of 8.5 months from surgery. After a comparison between the different treatment subgroups, patients treated with adjuvant SRT or adjuvant whole brain RT + simultaneous integrated boost of the surgical cavity had a better LC compared to patients receiving adjuvant whole brain RT alone or observation (1-year LC: 83% vs 56%, p < 0.001, Figure 2). No differences were found in terms of DIC and OS comparing all the postoperative approaches.

Conclusion SRT is confirmed to be an effective and safe treatment after surgery for brain metastases, with good LC and OS rates and a relatively low incidence of RN and LMD. Our results support the adoption of adjuvant SRT for resected brain metastases, although further evidence from larger retrospective studies and randomized trials is eagerly awaited in this setting.

PO-1122 Simultaneous integrated boost with spot scanning proton beam irradiation for meningiomas

C. Luetgendorf-Caucig 1 , E. Hug 2 , M. Pelak 1 , B. Flechl 1 , P. Fossati 1 , M. Momot 3 , A. Carlino 3 , C.L. Hajdusich 1 , P. Georg 4

1 MedAustron, Radiation Oncology, Wiener Neustadt, Austria; 2 MedAustron, Radiation Oncology, Wiener Neustast, Austria; 3 MedAustron, Medical Physics, Wiener Neustadt, Austria; 4 MedAsutron, Radiation Oncology, Wiener Neustadt, Austria

Purpose or Objective