ESTRO 2021 Abstract Book

S756

ESTRO 2021

Abi/Enz-treated mCRPC patients. Materials and Methods

We retrospectively evaluated Abi/Enz-treated mCRPC patients from 11 hospitals between 2011-2020. A descriptive and multivariate analysis of the data was carried out in order to establish the association of local treatment to the primary tumor and PSA variations at 4 and 12 weeks (expressed as 25% modifications, relative to baseline value at the start of Abi/Enz) with OS. Association with OS was analyzed using multivariate Cox regression and log-rank analyses. Spearman’s rho correlation coefficient (r) was calculated to evaluate the association between PSA changes at 4 and 12 weeks. Results We analyzed 640 mCRPC patients with a median follow-up of 30.2 months. Patients with previous local treatment to the primary tumor presented greater OS than untreated, HR 0.79 (0.64-0.96), p=0.02, without significant differences depending on the type of local treatment, radiotherapy (28.42 months; HR 0.97 (0.67- 1.4), p=0.867 and prostatectomy followed by postoperative radiotherapy (31.34 months; HR 0.74 (0.48-1.13), p=0.164. We found a detriment OS in patients with a 25% PSA rise at 4 weeks, (20.57 vs 28.78 months; HR 1.66 (1.3-2.13), p<0.001) and a 25% confirmed PSA increase at 12 weeks after starting treatment (15,87 vs 31,61 months; HR 2.64 (2.06-3.39) p<0.001). The percentage PSA decline at 4 weeks was significantly correlated with the percentage PSA change at 12 weeks (r.0.821; p<0.001). Conclusion Local treatment to the primary tumor can be established as a prognostic factor in mCRPC. PSA changes as early as 4 weeks after Abi/Enza initiation are highly associated with OS in mCPRC. Prospective multicentre validation studies are needed to confirm these findings. PD-0914 The role of locoregional RT in BCLC stage C hepatocellular carcinoma patients treated with sorafenib W.I. Chang 1 , B.H. Kim 2 , E.K. Chie 1 1 Seoul National University Hospital, Radiation Oncology, Seoul, Korea Republic of; 2 Seoul Metropolitan Government Seoul National University Boramae Medical Center, Radiation Oncology, Seoul, Korea Republic of Purpose or Objective This study aimed to investigate the clinical benefits of locoregional radiation therapy (RT) before, after, and concurrent with sorafenib therapy for Barcelona Clinic Liver Cancer (BCLC) stage C hepatocellular carcinoma (HCC) patients. Materials and Methods Patients treated with sorafenib for BCLC stage C HCC between January 2015 and December 2017 at two institutions were retrospectively reviewed. Patients received RT for either curative or palliative aims In this study, only RT to locoregional sites including primary HCC, portal vein tumor thrombosis, or regional lymph node metastasis were analyzed. Results Among 398 patients treated with sorafenib, 68 (17.1%) patients were treated with locoregional RT for BCLC stage C HCC. At a median follow-up of 9.5 months, median progression-free survial (PFS) and overall survival (OS) were 2.2 and 9.5 months, respectively. In the multivariate analysis, locoregional RT (HR 0.57; 95% CI, 0.42-0.79, p < 0.001) was associated with favorable OS. After 1:1 propensity score matching, patients who did not receive locoregional RT showed worse OS than those who received RT (median 9.6 months vs 15.7 months, p = 0.017). Upfront sorafenib and upfront locoregional RT did not show statistically significant difference in OS, whereas RT dose ≥ 50 GyEQD2 resulted in prolonged OS compared with RT dose < 50 GyEQD2. Conclusion Locoregional RT was significantly associated with longer survival in BCLC stage C HCC patients treated with sorafenib. Therefore, incorporating locoregional RT to these patients even after sorafenib failure could be considered to improve dismal prognosis of BCLC stage C HCC patients. PD-0915 SABR as a bridge therapy for HCC patients awaiting liver transplant L. spinelli 1 , R. Carlevato 1 , V. Chiofalo 1 , E. Gallio 2 , S. Gaia 3 , G. Rizza 4 , R. Faletti 5 , L. Molinaro 6 , M.G. Papotti 6 , R. Romagnoli 4 , G.M. Saracco 3 , P. Fonio 5 , G.C. Iorio 1 , A.S. Guarneri 1 , U. Ricardi 1 1 University of Turin, Department of Oncology, Radiation Oncology, Turin, Italy; 2 University of Turin, Department of Physics, Turin, Italy; 3 University of Turin, Department of Gastroenterology, Turin, Italy; 4 University of Turin, Department of Liver Surgery, Turin, Italy; 5 University of Turin, Department of Radiology, Turin, Italy; 6 University of Turin, Department of Pathology, Turin, Italy Purpose or Objective Hepatocellular carcinoma (HCC) patients awaiting transplant are at dropout risk because of tumor progression. Thus, bridging therapies have a pivotal role in this setting. When patients are not eligible for local therapies other than radiotherapy, Stereotactic ablative radiotherapy (SABR) is increasingly recommended. Herein, we aimed at analyzing its role within this clinical scenario. Materials and Methods Thirty-five patients (with 48 lesions) who underwent SABR between September 2012 and April 2020 at our Radiation Oncology Department while awaiting liver transplant (LT) were included in this retrospective analysis. Poster discussions: Poster discussion 32: Upper GI (pancreas, liver) 2

Results The SABR treatment aim was a "bridge" approach to LT for 26 patients while downstaging for 9. The median