Abstract Book

S793

ESTRO 37

2 Maastricht University, Medicine, Maastricht, The Netherlands 3 MAASTRO Clinic, Clinical Physics Research, Maastricht, The Netherlands Purpose or Objective The mainstay of rectal cancer treatment is surgery according to the total mesorectal excision (TME) principle. Unfortunately, TME surgery may result in significant long-term morbidity. In locally advanced tumors TME surgery is generally preceded by neoadjuvant radiotherapy or chemoradiotherapy as this has been shown to improve locoregional control. For 15-20% of patients, a clinical complete response (cCR) is seen after chemoradiotherapy. These patients can potentially be spared mutilating surgery through a watch and wait policy. Recent studies have shown that dose escalation by a radiation boost increases the complete response rate compared to the standard uniform dose. The boost dose to the tumor can be administered through external beam radiotherapy (EBRT) or through internal radiotherapy, the latter using different techniques like contact X-ray therapy (CXT), low-dose-rate (LDR) brachytherapy (BT) or high-dose-rate (HDR) BT. CXT is often mentioned as causing very little toxicity. However, very limited information is available concerning the treatment-related toxicity of these techniques. With this systematic review, we aim to summarize and compare the data that has been published concerning acute and late toxicity after CXT and/or BT for rectal cancer. Material and Methods The search on Pubmed was performed by two of the authors. All studies reporting toxicity after endorectal radiation techniques for rectal cancer were included and analyzed according to the PRISMA Checklist of items to include when reporting a systematic review and meta- analysis 2009 . Results 35 studies were included, resulting in 2591 patients for analysis. Direct comparison of the occurrence of toxicity by the different radiation techniques was hampered by various combinations of endorectal techniques, a lack of clear reporting of toxicity scores, dose prescription, technique used, and treated volumes. ≥ Grade 3 rectal toxicity was reported in 9 out of 480 patients having received only CXT. 12 out of 330 patients who clearly received only BT had ≥ Grade 3 rectal toxicity, and BT also caused Grade 3 urinary toxicity in one patient. Conclusion All techniques reported some ≥ Grade 3 toxicity. Notably, toxicity after CXT was confined to only the rectum. Unfortunately, few specific conclusions could be drawn regarding the dose related risk of toxicity for the various endorectal techniques due to missing information. Hence, recommendations were given for standard dose reporting for endorectal techniques to enable comparison of techniques in the future. EP-1461 Immune inflammation indicators in anal cancer patients treated with concurrent chemo- radiation P. Franco 1 , F. Montagnani 2 , F. Arcadipane 3 , C. Casadei 4 , K. Andrikou 5 , S. Martini 6 , G.C. Iorio 6 , M. Scartozzi 7 , M. Mistrangelo 8 , L. Fornaro 9 , P. Cassoni 10 , S. Cascinu 5 , U. Ricardi 6 , A. Casadei Gardini 4 1 Ospedale Molinette University of Turin, Department of Oncology- Radiation Oncology, Torino, Italy 2 ASL Biella, Department of Oncology- Medical Oncology, Biella, Italy

3 AOU Citta' della Salute e della Scienza, Department of Oncology- Radiation Oncology, Turin, Italy 4 Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori IRST IRCCS, Department of Medical Oncology, Meldola, Italy 5 Modena Cancer Center- University of Modena and Reggio Emilia, Department of Oncology/Hematology, Modena, Italy 6 University of Turin, Department of Oncology- Radiation Oncology, Turin, Italy 7 University of Cagliari, Department of Medical Oncology, Cagliari, Italy 8 University of Turin, Department of Surgical Sciences, Turin, Italy 9 Azienda Ospedaliero-Universitaria Pisana, Unit of Medical Oncology 2, Pisa, Italy 10 University of Turin, Department of Medical Sciences- Pathology Unit, Turin, Italy Purpose or Objective Systemic inflammatory response has been shown to reflect the promotion of angiogenesis, DNA damage and tumor invasion through up-regulation of cytokines. Several inflammation and immune-based prognostic scores, such as lymphocyte count, neutrophil-lymphocyte ratio (NLR) and systemic immune-inflammation index (SII) have been developed to predict survival and recurrence in different oncological settings. In the present study, we investigated the influence of different clinical prognostic factors, particularly the immune inflammation indicators, on clinical outcomes in anal cancer patients undergoing concurrent chemo-radiation (CT-RT). Material and Methods All patients in the present analysis had a histologically proven diagnosis of squamous cell carcinoma of the anal canal/margin and were treated with CT-RT according to the Nigro’s regimen. Pre-treatment SII (platelet x neutrophil/lymphocyte), NLR (neutrophil/lymphocyte) and PLR (platelet/lymphocyte) were obtained. Univariate and multivariate Cox models were set to explore the correlation between covariates and Progression-Free Survival (PFS) and Overall Survival (OS) Unconstrained univariate and multivariate logistic regression models were used to develop a nomogram able to predict the probability of response to CT-RT. Internal validation and calibration were performed using bootstrap method. Results A total of 161 consecutive patients were available for the analysis. Figure 1 shows the clinical variables predictive of PFS and OS. At univariate analysis SII was significantly correlated to PFS (HR:2.13;p<0.01) and OS (HR:1.70;p=0.046). NLR was significantly correlated to PFS (HR:1.13;p=0.05) but not to OS (HR: 1.15; p=0.06). Conversely, PLR was significantly correlated to PFS (HR:1.44;p<0.01) and OS (HR:1.43;p=0.02). For absolute values of platelets, neutrophils and lymphocytes, only platelet count was associated to PFS, but none of them was related to OS. On multivariate analysis SII retained a significant correlation to PFS (HR:1.43;p=0.0079), but not to OS (HR:1.13;p=0.15). On multivariate analysis with respect to OS, disease progression during CT-RT was the strongest predictive factor for both PFS (HR:41.36;p<0.0001) and OS (HR:42.15;p<0.0001). We developed a nomogram to predict the likelihood for disease progression. The final multivariate model included SII, basal hemoglobin values and clinical nodal involvement. The resulting nomogram showed remarkable predictive ability with a C-index of 0.847 (0.823-0.865) and a good calibration plot (Figure 2).