ESTRO 2021 Abstract Book

S880

ESTRO 2021

Português de Oncologia do Porto Francisco Gentil, Serviço de Física Médica, Porto, Portugal; 5 Instituto Português de Oncologia do Porto Francisco Gentil , Serviço de Física Médica, Porto, Portugal; 6 Instituto Português de Oncologia do Porto Francisco Gentil , Serviço de Radioterapia, Porto, Portugal Purpose or Objective Radiation therapy following resection of a brain metastasis increases the probability of disease control at the surgical site. This study aims to analyze our experience with postoperative stereotactic radiosurgery (SRS) and hypofractionated stereotactic radiotherapy (HFSRT) as an alternative to whole-brain radiotherapy (WBRT), characterize the population, determine their outcomes, and identify potential prognosis factors. Materials and Methods We retrospectively analyzed all patients treated in our department between 2013 and 2019, who, after surgical resection, underwent SRS/HFSRT to the tumor bed, deferring WBRT. The primary endpoint was local control (LC). Secondary endpoints were distant brain control (DBC), o verall survival (OS) and time to WBRT. Outcomes were estimated by the Kaplan-Meier method. Univariate (UVA) and multivariate (MVA) models were built to assess the influence of each variable. All statistical analysis was performed using the software R Thirty-eight patients with 39 surgical cavities met inclusion criteria with a median follow-up of 23.1 months. Most were male (n=20, 52.6%) with a median age of 59.5 (range, 38-71) and a single metastasis (n=34, 89,5%). The most common histologies included non-small cell lung cancer (n=16, 42.1%), breast (n=12, 31.6%) and renal cell carcinoma (n=3, 7.9%). The median cavity volume was 16,7cc (range, 2.1-54.3cc) and median PTV was 21.0cc (range, 3.20-65.0cc). Complete resection after surgery was achieved in 31 patients (79.5%). The most frequent prescription regimens were 27Gy in 3 fractions ( n =15, 38.5%) and 30Gy in 5 fractions ( n =20, 51.3%). Local failure was observed in 16 patients (41.1%), regional failure in 22 (57.9%), local or regional in 28 (73.7%) and distant failure in 8 patients (21.1%). Median OS was not achieved at the time of this analysis and OS rate at 1 and 2 years was 92.1% [95%CI, 83.9–100%] and 53.4% [95% CI, 58.2–77%] respectively. LC rate at resection cavity at 1 year and 2 years was 72.5% [95%CI, 59–88%] and 53.4% [95%CI, 37–75%] respectively. DBC at 1 and 2 years was 52.1% [95%CI, 38.3–70.8%] and 40.5% [95%CI, 26.6–62.1%]. Salvage radiotherapy was administered to 17 patients (44%) of which 6 (15.3%) received HFSRT. Five patients (13.1%) were proposed for another brain surgery. Median time to WBRT was 7.9 months (range, 1.66-47.16). No significant predictors have been found in multivariate analysis. Conclusion In this retrospective series, SRS/HFSRT administered to the resection cavity of brain metastases resulted in a 72% local control rate at 12 months. This value compares favorably with historic results with observation alone (54%) and postoperative WBRT (80–90%). SRS/HFSRT allowed postponing WBRT without compromising local control. v4.0.1. Results Purpose or Objective Secondary lesion developed in needle biopsy or surgical tract has been well documented in multiple primary tumours. Metastases resulting from seeding of surgery is considered a rare complication in gliomas. Aim of this study was to evaluate the benefit of surgical tract irradiation in high-grade gliomas to avoid tumour relapse on these sites. Materials and Methods We conducted a retrospective review of all patients with grade III and IV gliomas at our Radiation Oncology Department from January 2007 to November 2020. From an initial population of 52 patients, 40 patients were eligible for the analysis after exclusion of 12/52 patients because of inadequate follow-up or a pathology different than high-grade glioma. We identified 2 population of patients: those who had a CTV encompassing the surgical tracts ( N = 29) and those that have a CTV that did not encompass it ( N = 11). Then, we compared the pattern of relapse of these 2 populations. Noteworth, the inclusion of the surgical tract in the CTV is not a standard of care in our department and it only depended on the tumor localisation and on the marging that were added to the GTV to obtain the CTV and/or the PTV. The pattern of recurrence was evaluated by coregistering the first MRI showing a progression/recurrence, and we evaluated if the recurrence was at the surgical tract level or not. Results Mean age at diagnosis was 61 years. 85% of primary tumors were GBM. 15% of patients presented seizures as initial symptoms. After a median follow-up of 23 months, the median OS from diagnosis was 19 months. Progression or recurrences after radiation treatment were diagnosed in 30 patients, with a median PFS in all histological types of 19 months. Only 8 patients had a complete response at time of last follow-up. No patient presented an isolated recurrence observed in surgical tract. The relapses were infield (in the PTV) in 14/20pts, outfield in 1/20pts and infield and outfield in 5/20pt. Conclusion We cannot recommend extension of irradiation volume to include surgical tract because no benefit was observed in local control in our analysis PO-1059 LINAC-based radiosurgery for brain metastasis: patterns of recurrence and predictors of response B. Castro 1 , F. Sousa 1 , J. Rodrigues 2 , J. Lencart 3 , T. Viterbo 3 , T. Ramos 1 , A. Pires 1 , A. Aguiar 1 , A. Soares 1 , M. Lobão 4 , S. Conde 1 PO-1058 Should we include surgical tracts and scars in the CTV of High-grade gliomas? O. Santa Cruz 1 , S. Slimani 1 , L. Hirschi 1 , C. Tamburella 2 , P. Weber 1 , D. Dragusanu 1 , D.B. Berardino 1 1 Réseau Hospitalier Neuchâtelois, Radiation Oncology, La Chaux-de-fonds, Switzerland; 2 Hôpitaux Universitaires de Genève, Radiation Oncology , Geneva, Switzerland