ESTRO 38 Abstract book

S135 ESTRO 38

p=0.734), overall (84% vs. 82%; HR=0.92, p=0.845) and disease-free (70% vs. 72%; HR=0.87, p=0.682) survivals were not different between the LE and the TME groups at 5 years. No predictive factor of local recurrence was found, whereas ypT2-3 stage was independent factor of metastatic recurrence (HR=2.88, p=0.02). Conclusion The 5-year results of this multicenter randomized trial suggest the oncologic safety of the strategy in selected patients with small T2T3 low rectal cancer. OC-0274 5x5 Gy and consolidation chemotherapy vs. chemoradiation for rectal cancer: a phase III study K. Bujko 1 , X. On Behalf Of The Polish Colorectal Study Group 2 1 The Maria Sklodowska-Curie Memorial Cancer Center, Department Of Radiotherapy, Warsaw, Poland Purpose or Objective This study evaluated whether preoperative short-course radiotherapy combined with consolidation chemotherapy (CCT) is superior to chemoradiation in terms of R0 resection rate. Previously we reported no differences in R0 resection, complete pathological response, postoperative complications, late complications, disease- free survival, incidence of local failure and distant metastases after 3 years of median follow-up (Ann Oncol 2016, 27:834–42). However, in the short-course/CCT group, we observed lower acute radiochemotherapy- induced toxicity (75% vs. 83%, p=0.006) and 8% benefit (p=0.046) in overall survival at 3 years. The main aim of the current analysis is to find out whether benefit in overall survival is sustained with longer observations. Material and Methods Patients with fixed cT3 or cT4 rectal cancer were randomised either to 5x5 Gy and three cycles of FOLFOX4 given in tight sequence or to chemoradiation (50.4 Gy in 28 fractions combined with two 5-day cycles of bolus 5-Fu 325 mg/m2/day and leucovorin 20 mg/m2/day during the first and fifth week of irradiation along with five infusions of oxaliplatin 50 mg/m2 once weekly). The protocol was amended during accrual to allow oxaliplatin to be omitted in both groups. Results In total, 515 patients were eligible for analysis: 261 in the short-course/CCT group and 254 in the chemoradiation group. The median follow-up was 7.0 years (interquartile range 5.7–8.3 years). The benefit in overall survival at 3 years after short-course/CCT previously reported was also observed (71.6%, 95% confidence interval [CI] 66.1%–77.1% vs. 63.0%, 95% CI 57.1%–68.9%). However, this benefit disappeared later; at 8 years, overall survival was 48.8% in the short-course/CCT group vs. 48.6% in the chemoradiation group: hazard ratio (HR) 0.89 (95% CI 0.70– 1.14), p=0.35. The corresponding values for disease-free survival were 42.6% vs. 41.0%, HR 0.94 (95% CI 0.75–1.19), p=0.64. The cumulative incidences of local failure and distant metastases did not differ between the short- course/CCT group and the chemoradiation group, and after 8 years were 35.0% vs. 31.9%, (relative risk [RR]=1.08, 95% CI 0.70 - 1.23), p=0.59 and 35.5% vs. 33.3%, (RR=1.11, 95% CI 0.67 - 1.21), p=0.49, respectively. The rate of late complications in the short-course/CCT group was 21.5% vs. 21.2% in the chemoradiation group, p=0.58. Conclusion There was no difference in long-term overall survival between the short-course/CCT group and the chemoradiation group. Nevertheless, we suggest that benefits in short-term survival and acute toxicity favour short-course/CCT.

Conclusion The outcomes on 7-year relapse free survival and overall survival demonstrated no difference between hypofractionation versus conventional fractionation. A trend toward better local control was found after hypofractionation, whereas local control was statistically significant superior in patients with Gleason ≥8 tumors. These data on local control suggest that hypofractionation might be beneficial provided that high risk patients with subclinical metastasis at start of treatment are identified. OC-0273 Organ preservation after chemoradiotherapy for rectal cancer: 5-year results of the GRECCAR2 trial V. Vendrely 1 , P. Rouanet 2 , J. Tuech 3 , A. Valverde 4 , B. Lelong 5 , M. Rivoire 6 , J. Faucheron 7 , J. Mehrdad 8 , G. Portier 9 , J. Asselineau 10 , E. Frison 10 , Q. Denost 11 , E. Rullier 11 1 CHU de Bordeaux, Radiotherapy, Pessac, France ; 2 ICM, Surgery, Montpellier, France; 3 CHU Rouen, Surgery, Rouen, France; 4 Hospital Diaconesses Croix saint Simon, Surgery, Paris, France ; 5 Institut Paoli Calmettes, Surgery, Marseille, France ; 6 Centre Léon Bérard, Surgery, Lyon, France; 7 CHU Grenoble, surgery, Grenoble, France; 8 Centre Oscar Lambret, Surgery, Lille, France; 9 CHU Toulouse, surgery, Toulouse, France ; 10 ISPED, Statistics, Bordeaux, France; 11 CHU Bordeaux, Surgery, Bordeaux, France Purpose or Objective To evaluate the long term results at 5 years of the multicenter randomized trial comparing local excision (LE) vs. total mesorectal excision (TME) in good responders after chemoradiotherapy (CRT) for T2T3 low rectal cancer. Material and Methods From March 2007 to September 2012, 148 patients clinically good responders after CRT for T2T3 rectal cancer, size ≤ 4 cm, were randomized in 74 LE vs. 74 TME, 3 were excluded and 145 analyzed. In the LE group, 26 had a completion TME for ypT2-3, which was part of the protocol. Kaplan-Meier and Cox regressions were used to estimate and compare local and metastatic recurrence and survival at 5 years. Results Local recurrence (7% vs. 7%; hazard ratio (HR)=1.41, p=0.599), metastatic recurrence (18% vs. 19%; HR=0.86,

Proffered Papers: CL 6: Proffered papers Radiation and Targeted Agents