ESTRO 36 Abstract Book

S677 ESTRO 36 2017 _______________________________________________________________________________________________

86.0%, and 79.8%, respectively. One-year, 3-year, and 5- year cumulative OS were 97.8%, 93.5%, and 84.1%, respectively (fig.1).

REFERENCES:

1. Vuong et al. Contribution of conformal therapy in the treatment of anal canal carcinoma with combined chemotherapy and radiotherapy: Results of a phase II study. Int J Radiat Oncol Biol Phys 2003; 56(3): 823-31. EP-1272 Impact of Ki67 on pathological complete response rate after neoadjuvant CRT in cT3N0M0 rectal cancer D. Adua 1 , L. Giaccherini 2 , A. Guido 2 , D. Cuicchi 3 , F. Di Fabio 1 , F.L. Rojas Llimpe 1 , G. Macchia 4 , S. Cammelli 2 , L. Fuccio 3 , A. Ardizzoni 1 , A.G. Morganti 2 1 S.Orsola-Malpighi Hospital, Department of Medical Oncology, Bologna, Italy 2 University of Bologna, Radiation Oncology Unit- Department of Experimental- Diagnostic and Specialty Medicine - DIMES- Sant'Orsola-Malpighi Hospital, Bologna, Italy 3 University of Bologna, Department of Medical and Surgical Sciences - DIMEC, Bologna, Italy 4 Fondazione di Ricerca e Cura Giovanni Paolo II- Università Cattolica del Sacro Cuore, Radiotherapy Unit, Campobasso, Italy Purpose or Objective Multimodal therapeutic approach with pre-operative chemoradiation (CRT), conservative surgery +/- adjuvant chemotherapy (CT) is currently the standard treatment in patients with locally advanced rectal ca. The possibility to predict tumor response before chemoradiation could be useful to tailor neoadjuvant treatment. Therefore, aim of this analysis was to correlate the expression of Ki67 with pathological complete response (pCR) rate after CRT in an homogeneous population of patients with cT3N0M0 rectal carcinoma. Material and Methods We retrospectively analysed the pre-treatment biopsies of a subgroup of patients (pts) witch cT3N 0 rectal ca. The expression of Ki-67 was evaluated. Radiotherapy was delivered with 3-D conformal technique (total dose: 50.4 Gy, 1.8 Gy/fraction) concurrently with CT (Capecitabine: 31%, 5-Fluorouracil: 17%, 5-Fluorouracil plus Oxaliplatin: 52%). All pts underwent surgery 6-8 weeks after CRT. Adjuvant CT was performed in 37 (76%) pts. DFS and OS were estimated by Kaplan-Meier method. Using as cut-off value the median value of ki-67 expression (91.3%, range 54.1%-99.9%), we stratified pts into two subgroups to test a possible correlation with pCR. Results Forty-eight pts were treated from March 2002 to October 2011 [M/F: 32/16; median age: 70.5, range: 43-84]. The median follow-up was 61.5 months (range: 2-136). Ten pts achieved a pCR (20.8%). No significant differences were observed based on Ki67 value (lower Ki67: 62.5% pCR; higher Ki67: 37.5% pCR); Fisher's Exact test: p=0.345). One-year, 3-year, and 5-year cumulative DFS were 97.9%,

Conclusion In this retrospective analysis no significant correlation was observed between Ki67 expression and pCR rate after preoperative chemoradiation. The small sample size and heterogeneity in neoadjuvant and adjuvant treatment could explain this result. EP-1273 Stereotactic body radiation therapy (SBRT) for pelvic re-irradiation Y. Augustin 1 , C. Chaw 1 , N. Van As 1 , K. Aitken 1 1 Royal Marsden Hospital Trust & Institute of Cancer Research, Radiotherapy, London, United Kingdom Purpose or Objective Re-irradiation of recurrent pelvic disease remains a challenging clinical problem. SBRT is an attractive modality for re-irradiation which is being increasingly utilised in carefully selected patients. However there remains uncertainty around clinical toxicity, efficacy and maximum safe cumulative doses to pelvic organs at risk (OARs). The primary aim of this retrospective study was to evaluate treatment related toxicity in patients receiving SBRT with the Cyberknife platform for pelvic re-irradiation at our institution. Secondary objectives were to evaluate efficacy by analysis of local control (LC), distant progression free survival (DPFS) and overall survival (OS) parameters. Material and Methods Patients receiving re-irradiation with SBRT to pelvic targets within a previously irradiated external beam radiotherapy (EBRT) field were retrospectively identified. Patients treated with prior pelvic brachytherapy were excluded. Details on primary site, previous EBRT and re- irradiation dose, toxicity, local control and survival were obtained on review of the hospital records. Acute (≤3 months) and late toxicity data were retrospectively collected and assessed using CTCAE v4.0. Local and distant progression free survival were calculated from the date of SBRT to the date of radiological progression using standard RECIST criteria (v1.1). Results