ESTRO 2022 - Abstract Book

S57

Abstract book

ESTRO 2022

PD-0080 Post-operative radiosurgery for brain metastases: clinical and dosimetric evaluation

V. Pinzi 1,2 , A. Romeo 1 , M. Marchetti 1 , S. Morlino 1 , L. Fariselli 1

1 Fondazione IRCCS Istituto neurologico Carlo Besta, Radiotherapy Unit, Neurosurgery Department, Milan, Italy; 2 University of Milan Bicocca, Neuroscience, MILANO, Italy Purpose or Objective to explore the rate of local control and the risk of brain radiation necrosis in both single fraction (SF) and multi fraction (MF) approaches in the setting of post-operative radiosurgery (SRS) for brain metastases. Materials and Methods we retrospectively analyzed clinical, dosimetric and radiological data of 48 patients (52 cavities) who underwent post- operative SRS for brain metastases from April 2011 to May 2020 at our Institute. Survival and local control (LC) were correlated to both clinical and dosimetric data. Results median age at SRS time was 55 (range 26-79). 20/52 patients had NSCLC histology, 15/52 breast histology, 4/52 melanoma, 3/52 had colon carcinoma, 10/52 had other histologies. 22/52 patients received SF-SRS (range 14-20 Gy/1 fraction); 30/52 patients received MF-SRS (range 21-24 Gy/3 fractions). Patients with prior whole brain radiation therapy (WBRT) were excluded. After a median radiologic follow up of 30 months, the 1-year cumulative LC rates were 86% and 90% in the SF- SRS and in the MF-SRS groups, respectively. Median time to failure from CK was 25 months (range 6-80 months). Radiologic pattern of local recurrences was in-field in 92 % of patients. Three patients (13%) in the SF-SRS group and only 1 (3%) in the MF-SRS group experienced brain radiation necrosis. These 3 cases of radiation necrosis in the SF-SRS group, had a V12Gy (brain volume receiving 12 Gy) value > 5 ml. However, 2 out of these 3 occurred after cavity re-irradiation. The only case of brain radiation necrosis in the MF-SRS group had V20Gy > 20 ml. No other toxicities > G2 were reported. At last follow- up, 25/52 patients (48%) were alive. 15/27 of them died because of brain progression disease (PD), 9/27 because of extra- cranial PD, 1 for both brain and extra-cranial PD, 2/27 patients as a consequence of other causes. Median OS at last follow- up was 44.5 months (95% CI 22.2-77.2). Twelve- and 24-month median OS was 84.6%(95% CI 71.5%-92.0%) and 63.5%(95% CI 48.3%-75.3%), respectively. Lesion volume and histology did not affect OS nor local control. Stable extracranial disease was significantly correlated with better OS (77% versus 17%). Conclusion our analysis shows that both MF-SRS and SF-SRS approaches provide good local control without relevant toxicities for post- operative brain metastases treatment. MF-SRS setting seems to be associated with a lower risk of brain radiation necrosis. 1 Gustave Roussy, Radiation oncology, Villejuif, France; 2 Gustave Roussy, Drug Development Department (DITEP) , Villejuif, France; 3 Gustave Roussy, Biostatistics , Villejuif, France; 4 Gustave Roussy, Radiation oncology , Villejuif, France; 5 Gustave Roussy, Radiation Oncology, Villejuif, France Purpose or Objective Immunotherapy, alone or in combination, is being tested in many squamous cell carcinoma (SCC) types. Stereotactic body radiation therapy (SBRT) co-administered with immunotherapy may lead to an enhanced tumor response outside of the primary treatment field. We report here the phase I safety part of the ABIMMUNE (Durvalumab [D]+-Tremelimumab [T]+SBRT) trial. Materials and Methods This phase I single arm study included a two-step safety run (dual combination of D+SBRT then triple combination of D+T+SBRT). Durvalumab (1500 mg IV every 4 weeks (Q4W), for up to 13 dose) +- tremelimumab (75mg/Q4W for up to 4 doses, then modified following manufacturer instruction to 300 mg IV single dose at C1D1) and SBRT (9 Gy x 3 fractions from C1D15) were administered in metastatic head and neck, lung, oesophageus, cervix, vagina, vulva or anus SCC patients. The phase II part (n=55) is ongoing. Each study step was, started after dose-limiting toxicity (DLT, based on CTCAE-V4, within 8 weeks from C1D1) assessment of combination-related toxicities. Results Twenty patients (n=9 D+SBRT; n=11 D+T+SBRT, n=3 T Q4W and n=8 T single dose) were included in this phase I part at a single center. Most patients were female (65%), the median age was 54 years, most represented primary tumors were esophagus (42%), anal (26%) and cervix (16%) SCC and all patients had received prior (median: 2 lines) systemic treatments. In the D+SBRT group, one patient experienced a DLT of Grade (G) 3 colitis. In the D+T+SBRT group: two patients experienced (T Q4W: n=1 and T single dose: n=1) DLT of G3 colitis (both with G3 diarrhea and one with G3 abdominal pain). Overall, 24 G3-4 adverse events (AEs) were reported in the D+SBRT (n=12, gastrointestinal (GI) disorders being the most frequent, 4/12, 33%) and D+T+SBRT groups (n=12, GI disorders being the most frequent, 7/12, 58%). No toxicity-related death was, observed. PD-0081 SBRT, Durvalumab+-Tremelimumab in metastatic SCC: preliminary safety results of a phase I/II trial A. Levy 1 , R. Bahleda 2 , C. Brard 3 , J. Durand-Labrunie 4 , A. Hollebecque 2 , E. Deutsch 5

Conclusion