ESTRO 2021 Abstract Book

S380

ESTRO 2021

hospitalization was also significantly longer in the TTB≥ 60 vs TTB<60 group; 30.6 vs 14.3 days (p<0.01) After surgical resection, the mean OS was 25 months for patients with a TTB ≥60, compared to a mean OS of 34 months for patients with a TTB below 60 (p=0.05). Predictors for a TTB ≥ 60 were age (at start treatment) (OR: 1.04, 95%CI 1.01-1.07), Mean Lung Dose (MLD) (OR: 1.10, 95%CI 1.01-1.19),and parameter to correct for resection (Y/N) (OR: 2.68, 95%CI 1.21-6.02), which resulted in the model as presented in Table 1 . Conclusion A TTB ≥60 was best predicted by age, MLD and resection (Y/N) and results in significant worse overall survival and longer hospital and ICU stay. References: 1. 1. Hobbs B.P., Thall P.F., Lin S.H. Bayesian Group Sequential Clinical Trial Design using Total Toxicity Burden and Progression-Free Survival. J. R. Stat Soc Ser C Appl Stat. 2016 Feb;65(2):273-297.

Table 1. Multivariable prediction model for TTB≥ 60.

PH-0496 incidence and pattern of LRR in esophageal cancer patients treated with iCT followed by neoadj CTRT G. rossi 1 , N. Simoni 2 , R. Rossi 2 , M. Venezia 2 , M. Pavarana 3 , P. Del Bianco 4 , C. Cavedon 5 , G. De Manzoni 6 , R. Mazzarotto 2 1 Azienda Ospedaliera Universitaria Integrata Verona, Radiotherapy , Verona, Italy; 2 Azienda Ospedaliera Universitaria Integrata Verona, Radiotherapy, Verona, Italy; 3 Azienda Ospedaliera Universitaria Integrata Verona, Oncology, Verona, Italy; 4 Istituto Oncologico Veneto IOV - IRCCS, Clinical Research Unit, Padova, Italy; 5 Azienda Ospedaliera Universitaria Integrata Verona, Medical Physics, Verona , Italy; 6 Azienda Ospedaliera Universitaria Integrata Verona, General and Upper G.I. Surgery, Verona, Italy Purpose or Objective To evaluate the incidence and pattern of failure and to define a dosimetric map of loco-regional recurrence (LRR) for patients (pts) with locally advanced esophageal cancer (EC) treated with induction chemotherapy, followed by neoadjuvant chemo-radiotherapy, and surgery. Materials and Methods ECs treated with trimodality therapy between 2008 and 2019 at our Institution were retrospectively reviewed. The site of first failure was documented as distant, LRR or combined (distant and LRR). LRR included anastomotic/perianastomotic failure (AR) and regional lymph node recurrence (NR). A dosimetric analysis was performed to correlate LRRs to radiation target volumes, using both rigid (RIR) and deformable image registration (DIR) to better compare computed tomography (CT) anatomy. A cause specific hazard model was used to evaluate prognostic factors for recurrence. Results 126 EC pts (78 adenocarcinoma, 48 squamous cell carcinoma; 115 cT3/4; 110 cN+; median age 63 years) were eligible for the analysis. The neoadjuvant chemo-radiotherapy (nCRT) schedule consisted of an induction phase of weekly administered docetaxel, cisplatin, and 5-fluorouracil (TCF) for 3 weeks (94.4% of cases, or weekly paclitaxel and carboplatin (PC) in 5.6%), followed by a concomitant phase of weekly TCF (93.7% of cases, PC in 6.3%) for 5 weeks with concurrent radiotherapy (50-50.4 Gy in 25-28 fractions). Conformal (3D- CRT) and intensity modulated (IMRT) radiation techniques were adopted in 55.6% and 44.4% of cases, respectively. At the time of surgery, pCR was achieved in 49.2% of pts, with a 98.4% of R0 resection rate. With a median follow-up of 64 months (95% CI: 56-72.7), median overall survival (OS) and progression free survival (PFS) were 97.4 months (95% CI: 57.5-NE) and 47.5 months (95% CI: 29.5-117), respectively. 56 (44.4%) pts experienced recurrent disease, with a distant, combined, and isolated LRR pattern in 37 (66.1%), 11 (19.6%), and 8 (14.3%) cases, respectively. Concerning the 19 (15.1%) LRRs, 12 (63.2%) pts had NR, 6 (31.6%) AR, and 1 (5.2%) NR+AR. The dosimetric evaluation showed that 4 LRRs occurred as in-field (mean recurrence D mean 27.8±23.1 Gy/D max 50.8±0.6 Gy), 2 as marginal (D mean 3.7±4.0 Gy/D max 33.2±16.8 Gy), and 13 as out-of-field failure. The 5-years cumulative incidence of LRR was 9% in pathological complete response (pCR) vs 21.5% in non-pCR (HR 0.24, p = 0.0078), 31.9% in pN+ vs 9.6% in pN0 (HR 6.82, p = < 0.0001), and 9.3% in ³ 60 years vs 27% in < 60 years (HR 0.32, p = 0.0155), 0.0% in cT1/2 vs 16.8% in cT3/4 (NE) and 0.0% in female vs 18.5% in male pts (NE). Conclusion LRR represents an uncommon event in ECs treated with trimodality therapy, suggesting a pivotal role of preoperative radiotherapy in reducing the risk of loco-regional failure. pCR, pN0, age > 60 years, cT1/2 and female gender were associated with lower rate of LRR. PH-0497 Local treatment including RT for HCC with portal invasion: a matched analysis using nationwide data C.H. Rim 1 , H.A. Lee 2 1 Korea University Ansan Hospital, Radiation Oncology, Ansan, Korea Republic of; 2 Inje Paik Hospital, Gastroenterology, Seoul, Korea Republic of

Purpose or Objective Local treatment including radiotherapy (LRT) has been applied as an effective palliation for hepatocellular