ESTRO 38 Abstract book

S787 ESTRO 38

20.9% patients, mean and median time to LR was 12.2 and 7.8 months. Males are more likely to have colostomy for LR (HR=3.59, P= 0.014). Tumor stage but not node stage is also associated with higher LR (HR=10.4 for T4 vs T1). There is no correlation between T and N stage with distant metastases. Active smokers at diagnosis/treatment are more likely to undergo a colostomy procedure for LR than former smokers or non-smokers (HR 7.793; P= 0.0053 and HR 2.99; P= 0.2719). Smoking status has no impact on distant failure. Elderly patients have a worse CSS (HR 1.08; P<0.0001) and a significantly higher risk of 90-day mortality after treatment (OR = 1.20; p< 0.0015) with a 26 folds increase risk (p= 0.0031) if patient is older than 71 years.

5 (5%) had local/locoregional failure. Pathologic complete response (pCR) was defined as the absence of viable cancer cells in the resected specimen (ypT0N0). pCR was achieved in 17% of all cases (18/106). According to TRG system, grade 0-1 and grade 2-3 responders were 45 patients (42.5%) and 61 patients (57.5%), respectively. The mean ± SD SUVmax, SUVmean, MTV and TLG were 16.9 ± 9.6 (range, 3.6 - 60.2), 9.6 ± 6.3 (range, 2.4 - 49.2), 24.7 ± 26.4 cm³ (range, 2.8 -160.5 cm³) and 268.7 ± 474.5 (range, 21.8 -3,092.0) for the entire group, respectively. There was a weak correlation between SUVmax of primary rectal tumors and MTV (Pearson correlation coefficient [r] = 0.238; p < 0.001). On the other hand, SUVmax of primary rectal tumors and TLG were significantly correlated (r=0.538; p < 0.001). Neither SUVmax nor SUVmean were affected by patient and tumor characteristics. On the other hand, volumetric FDG-PET parameters, such as MTV and TLG, were significantly higher in patients with larger tumors (≥3 cm) and middle rectum located tumors compared to the patients with smaller tumors (<3 cm), and proximal or distal rectum located tumors. Posttreatment extensive stage of disease (p=.013), absence of concomitant CT (p=.012), MTV ≥14.65 cm3 (p=.008), and TLG ≥117.00 (p=.023) were unfavorable prognostic factors for OS on multivariate analysis. Conclusion Although FDG-PET is not a standard imaging modality for the treatment of rectal cancers a negative effect of high MTV and TLG on OS was shown in our study. We should consider more intense treatment approaches for tumors with high MTV and TLG values. EP-1450 How smoking status impacts patients undergoing radiochemotherapy for anal canal carcinoma? L. Grandjean 1 , M. Lamande 1 , E. Gonne 2 , D. Van Daele 3 , J. Collignon 2 , M. Polus 3 , C. Loly 3 , L. Seydel 4 , J. Vanderick 1 , P. Coucke 1 , P. Martinive 5 1 CHU de Liege, Radiation therapy, Liege, Belgium ; 2 CHU de Liege, Medical Oncology, Liege, Belgium ; 3 CHU de Liege, Gastroenterology and Digestive Oncology, Liege, Belgium ; 4 CHU de Liege, Biostatistics- SIME, Liege, Belgium ; 5 Institut Jules Bordet, Radiation therapy, Brussels, Belgium Purpose or Objective Radiochemotherapy (RCT) is the standard of care for Anal Canal Squamous Cell Carcinoma. Although, tobacco consumption during RTC decrease overall survival (OS), cancer specific survival (CSS) and disease-free survival (DFS) in many tumors but it has never been demonstrated in anal cancer. The aim of this study is to compare the results of a tertiary university hospital in terms of colostomy-free survival (CFS), OS, CSS, DFS and to identify prognosis factors in regards to tobacco consumption. Material and Methods We retrospectively identified 110 patients, with histologically proven SCC of anal canal treated with RCT in our institution between 01/2008 and 12/2017. Patients received 59.4Gy in 33 fractions concomitantly with 5FU and MMC either based on RTOG (45Gy to the pelvic + 14.4Gy for the boost) or EORTC (36Gy to the pelvic + 23.4Gy for the boost) protocol with one week gap before the boost. Results Most patients presented locally advanced tumor (57.3% of stage III, table 1). Patients benefit from the RTOG and EORTC treatments in 54% and 46 %, respectively. With a median follow-up of 40.6 months (0.3 – 114.7), the 3- and 5-year OS are 73.5% (95% CI, 63.3%-81.2%) and 63.4% (95% CI, 51.6%-73.1%) and for CSS, 81.7% (95% CI, 72.4%-88.1%) and 74.2% (95% CI, 62.7%-82.7%). The 3- and 5-year DFS are 72% (95% CI, 61.9%- 79.8%) and 68.6% (95% CI, 57.8%- 77.2%) and for CFS, 81.9% (95% CI, 72.5%- 88.4%) and 79.9% (95% CI, 69.7%-87.1%). Local recurrence (LR) occurred in

Conclusion For the first time in the SCC of anal cancer, we pointed out tobacco consumption as a negative prognosis factor for LR. We also identified a cut-off of 71 years old for treatment related mortality. Worth noting the homogeneity of the cohort in a retrospective study thanks to institutional treatment protocol. The vast majority of patients presented T3/T4 and positive clinical nodes explaining an OS slightly lower than those observed in clinical trials with less advanced tumors. The CSS and the CFS are in accordance with the literature. To conclude, we should advise patients to stop tobacco consumption during treatment, and we should submit all patients more than 71 years old to an oncologic geriatric evaluation. EP-1451 Impact of tobacco smoking on patient’s outcome after (chemo)-radiotherapy for anal cancer L. Jacques 1 , H. Christophe 1 , E. Isabelle 2 , A. Laurent 3 , G. Gael 4 , G. Jean-Marc 5 , G. Sophie 1 , A. Thomas 5 , V. Alain 6 , C. Pierre 7 , L. Quero 1 1 Saint-Louis Hospital, Radiation Oncology, Paris, France ; 2 Croix Saint Simon Hospital, Proctology, Paris, France ; 3 Bichat Hospital, Proctology, Paris, France ; 4 Bichat Hospital, Gastroenterology, Paris, France ; 5 Saint-Louis Hospital, Gastroenterology, Paris, France ; 6 Croix Saint