ESTRO 2021 Abstract Book

S1051

ESTRO 2021

Two coplanar arcs were employed for VMAT delivery. Dosimetric results were consistent in term of both target coverage and normal tissue sparing. In regard to dosimetric findings, mean V40Gy of bladder were 11% (range 5-21.3%) and 16.5% (range 2.2-63.9%) in VMAT-SIB and VMAT-SB group, respectively; mean V45Gy of bowel were 27.8cc (range 0.5-97 cc)and 43.2 cc (range 1.9-252.9 cc) in VMAT-SIB and VMAT-SB group, respectively. At 3 months, a complete response was observed in 80% of pts in VMAT-SIB group, and in 91% of pts in VMAT-SB. Finally, in VMAT-SIB group OS rate was 95% with a mean follow-up of 14 months (3-36 months), while it was 77% in VMAT-SB with a longer mean follow-up of 44 months (3-120 months). Conclusion VMAT-SIB was feasible, safe, and effective. There was a dosimetric advantage in VMAT-SIB group for bladder and bowel dose volume histogram; however, there were not clinical differences in terms of acute toxicity. Larger accrual and longer follow-up are warranted in order to understand local control and survival benefit. PO-1273 Title: Impact of HPV infection in anal carcinoma patients treated with definitive chemo- radiation G. Veillon Contreras 1 , I.D. Perrot Rosenberg 2 , J.A. Solis Campos 1 , B. Tudela Staub 3 , G. Lazcano Alvarez 1 , J. Olivares Gonzalez 1 1 Hospital Carlos Van Buren, Servicio de Oncologia, Valparaiso, Chile; 2 Hospital Carlos Van Buren, Servicio de Oncología, Valparaiso, Chile; 3 Hospital Carlos Van Buren, Servicio de Oncologia , Valparaiso, Chile Purpose or Objective The aim of this study is to describe and analyze the treatment characteristics and outcomes of localized anal carcinoma patients treated at our facility, as well as determining human papilloma virus (HPV) infection by p16 immunohistochemistry (IHC) and its impact in survival. Materials and Methods We performed a retrospective cohort study including patients treated for localized anal carcinoma at our facility (Tis-T4 N0-3 M0) from 2008 to 2015 with chemoradiation or radiation alone with a curative intention. Histologic confirmation was mandatory. IHC determination of p16 and other HPV infection markers such as koylocites or condylloma morphology were centrally evaluated at our institution. Survival data was evaluated using the Kaplan Meier method. All patients were treated using ≥ 6MV 3DCRT. Different chemotherapy schemes were delivered concomitantly according to clinicians’ preference and patient’s characteristics. Results 65 patients from 8 different referring institutions were included with the previous approval of our Institutional Review Board. Median prescribed dose was 54 Gy (IQR 54-54) to the primary tumor, 45 Gy to pelvic lymph nodes (IQR 45-45 Gy) and 36 Gy to inguinal lymph nodes (IQR 36-45) with an additional boost to adenopathy depending on size (more or less than 2 cm). Concomitant chemotherapy was delivered in 78.4% of patients, with weekly cisplatin being the most common prescribe drug (84.3%). Median follow-up time was 41 months (IQR 16-68). 3-year PFS and OS for the entire cohort were 61.2% (CI 95% 47-72) and 67.5% (CI 95% 54-77) respectively. HPV presence was assessed through p16 IHC in 36 patients (55.4%) with a 63.9% positivity rate. Koilocytes were described in 47.2% of patients and condyloma morphology in 41.6% of the analyzed biopsies. 5-y Overall survival was 44.8% (CI 95% 17-69) for p16 (-) patients and 57.4% (CI 95% 30-77) for p16(+) patients (p = 0.65). Conclusion p16 IHC determination offers important prognostic information for localized anal carcinoma patients. Even if statistical significance to support an impact in overall survival in our series was not reached, a trend towards better prognosis in HPV (+) patients encourages further studies involving larger cohorts to explore this finding and it’s future impact in therapeutic decision making. PO-1274 Impact of pretreatment anemia in patients with rectal cancer treated with chemoradiotherapy R.M. Niespolo 1 , S. Terrevazzi 2 , R. Colciago 3 , A. Romeo 3 , M. Midulla 3 , F. Puci 3 , P. Pacifico 3 , S. Arcangeli 4 1 Radiation Oncology, H.San Gerardo, ASST Monza, Department of Radiation Oncology, ASST Monza, University of Milan Bicocca, Milan, Italy , Monza, Italy; 2 Radiation Oncology, H. San Gerardo ,ASST Monza, Department of Radiation Oncology, ASST Monza, University of Milan Bicocca, Milan, Italy , Monza, Italy; 3 Radiation Oncology, University of Milan Bicocca, Department of Radiation Oncology, ASST Monza, University of Milan Bicocca, Milan, Italy , Monza, Italy; 4 Radiation Oncology, H.San Gerardo, ASST Monza, University of Milan Bicocca, Department of Radiation Oncology, ASST Monza, University of Milan Bicocca, Milan, Italy , Monza, Italy Purpose or Objective To retrospectively assess the relationship between pretreatment anemia and clinical outcomes in patients who underwent neoadjuvant chemoradiotherapy for locally advanced rectal cancer (LARC) Materials and Methods Pre-treatment blood hemoglobin (Hb) levels were measured in a cohort of 140 LARC patients, and their correlation with local control (LC), overall survival (OS), and disease-free survival (DFS) were analyzed. Anemia was defined as the lowest quartile for both males and females. Survival rates were estimated with Kaplan-Meier analysis, and univariable and multivariate Cox proportional hazard ratios were used to assist in risk stratification Results Median follow up was 39 months (range 18-60 months). The average pre-treatment Hb level was 134 g/L (128 g/L in women , 137 g/L in man). Of 140 patients, 14 females and 16 males were found anemic. Overall, 2-y OS was decreased in anemic patients (64% vs 91%; p= 0.021), who also reported higher positive margins and local recurrence rates (36% vs 15%; p=0.021 and 38% vs 7%; p= 0.003), respectively. After adjusting for age, gender, stage, comorbidities, pre-treatmemt anemia in female patients was significantly associated with lower rates of OS (69,2 % vs 91,7%; p=0.022); DFS (64,2 % vs 91,1 p= 0.021 ) and local control (19,4% vs 30,8 %; p=0,011).