ESTRO 38 Abstract book

S429 ESTRO 38

underwent surgery between May 2014 and May 2016 after an interval of ≥6 weeks were included. Missing values were replaced by multiple imputation. Differences in baseline characteristics between SCRT-delay and CRT were evaluated by X 2 -test for categorical variables and t-test for continuous variables. The association between the different types of neoadjuvant treatment and postoperative complications was analyzed by multivariable logistic regression. Results 2,888 patients with LARC were included; 333 patients were treated with SCRT-delay and 2,555 with CRT. Mean age was higher in the SCRT-delay group compared to the CRT group (73.87 vs. 64.33, p<0,001). Also, prevalence of comorbidities was higher in the SCRT-delay group (81% vs. 66%, p<0,001). There were no statistically significant differences in tumor stage, surgical approach, the occurrence of postoperative complications, length of hospital stay or length of ICU stay. Patients in the SCRT- delay group more often received a permanent colostomy (p < 0.001).

significantly correlated with biological equivalent dose (BED) with a significant better LC when BED was ≥75 Gy (p<0.0001). Moreover, in multivariate analysis, LC was significantly higher in lesions with a Planning Target Volume (PTV) volume <42 cm 3 and treated with a BED ≥75 Gy. Patients with Karnofsky performance status (KPS) <90 showed a significantly higher out-field progression than the ones with KPS ≥90.

Conclusion Patients with oligometastatic CRC are considered candidates for curative treatment because long-term survival can be expected. Recent studies have shown that SRT in oligometastatic CRC is an excellent option for local treatment of metastases with a good outcome and low toxicity profile. Our study confirms that SRT is an effective treatment with low treatment-associated morbidity. It should be considered as a valid option for properly selected patients. Further studies should be focused to clarify which patient subgroup will benefit most from this treatment modality. Furthermore, researchers should aim to define the optimal dose in order to improve tumor control while maintaining low toxicity profile. PO-0820 Effect of short-course radiotherapy on postoperative complications in locally advanced rectal cancer S. Hoendervangers 1 , C. Sparreboom 2 , H. Van Grevenstein 3 , L. Verkooijen 1 , J. Lange 2 , P. Doornebosch 4 , M. Intven 1 1 UMC Utrecht, Radiotherapy, Utrecht, The Netherlands ; 2 Erasmus MC, Surgery, Rotterdam, The Netherlands ; 3 UMC Utrecht, Surgery, Utrecht, The Netherlands ; 4 IJsselland hospital, Surgery, Capelle a/d IJssel, The Netherlands Purpose or Objective Neoadjuvant short-course radiotherapy (5x5 Gy) with a prolonged interval to surgery (SCRT-delay) is regularly used as an alternative for neoadjuvant chemoradiation (CRT) in frail patients with locally advanced rectal cancer (LARC). However, evidence based data on management of LARC in the frail population is scarce. Consequently, there are no clear guidelines for the treatment of this group, and decision-making for the type of neoadjuvant therapy differs per center. With the increasing aging population, there is an urgent need for more evidence to justify the choice of neoadjuvant treatment in frail patients with LARC. Therefore, the aim of this study is to investigate the patient characteristics on which treatment deviation is based and to assess the effect on postoperative outcomes. Material and Methods This is an observational study with data from the Dutch ColoRectal Audit (DCRA), a national audit in which clinical outcomes of patients undergoing primary colorectal surgery are registered. Non-metastatic LARC patients who

Conclusion Despite the higher age and the higher prevalence of comorbidities, postoperative complications were not significantly higher in the SCRT-delay group. Short-course radiotherapy was not associated with increased postoperative complications and seems to be a good alternative neoadjuvant treatment option for frail LARC patients. PO-0821 Long-term outcome of an organ preservation strategy following chemoradiotherapy in rectal cancer E. Palazzari 1 , A. Lauretta 2 , F. Navarria 1 , R. Innocente 1 , C. Bellucco 3 , C. Bampo 4 , L. Balestreri 5 , F. Matrone 1 , G. Fanetti 1 , A. Revelant 1 , R. Cannizzaro 6 , V. Canzonieri 7 , A. Buonadonna 8 , J. Polesel 9 , G. Bertola 10 , A. De Paoli 1 1 Centro di Riferimento Oncologico CRO-IRCCS- Aviano- Italy, Radiation Oncology, Aviano, Italy ; 2 Centro di Riferimento Oncologico CRO-IRCCS- Aviano- Italy, Surgical Oncology, Aviano, Italy ; 3 Centro di Riferimento Oncologico CRO- IRCCS- Aviano-Italy, Surgical Oncology, Aviano, Italy ; 4 Centro di Riferimento Oncologico CRO - IRCCS- Aviano-Italy, Nuclear Medicine, Aviano, Italy ; 5 Centro di Riferimento Oncologico CRO - IRCCS- Aviano- Italy, Radiology, Aviano, Italy ; 6 Centro di Riferimento Oncologico CRO - IRCCS- Aviano-Italy, Gastroenterology, Aviano, Italy ; 7 Centro di Riferimento Oncologico CRO- IRCCS- Aviano- Italy, Pathology, Aviano, Italy ; 8 Centro di Riferimento Oncologico CRO - IRCCS- Aviano-Italy,