ESTRO 2022 - Abstract Book

S1122

Abstract book

ESTRO 2022

Chemoradiotherapy is the standard of care for non metastatic anal cancer. Despite a good prognosis, some patients will present relapses during follow-up. The aim of this study was to identify predictive factors of relapse on pre-therapeutic 18F-PET/CT. Materials and Methods 122 patients with PET/CT who underwent radio-chemotherapy for ASCC between February 2008 and April 2018 were retrospectively analyzed. Two regions of interest ( Gross Tumoral Volume for tumor and metastatic lymph nodes) were segmented. Morphological and PET-related features (intensity; volumes; radiomics) were extracted with the Quantimage TM Platform. Kaplan Meier curves and Cox proportional hazards regression model were used to find associations between these parameters and local control (LC), locoregional control (LRC), progression-free survival (PFS), distant metastatis-free survival (DMFS) and overall survival (OS). Results Median follow-up was 48 months (range : 1,93 – 143). LC, LRC, OS, PFS, DMFS rates were respectively 79%, 73%, 69%, 50% and 69% at 5 years. In multivariate analysis, an altered performance status (PS2 versus PS0) was significantly associated with worse OS [HR 4,73 (95% IC : 1,45 – 15,49), p = 0,0008], PFS [HR 2,92 (95% IC: 1,07 – 7,96), p = 0,014] and DMFS [HR 4,30 (95% IC : 1,33 – 13,92), p = 0,002]. A high pre-treatment Tumoral Lesion Glycolysis (TLG) of the primary tumor (> 65,2) with an absolute SUV threshold ≥ 2,5 was predictive for worse OS [HR 2,49 (95% IC : 1,29 – 4,82), p = 0,0068] and DMFS [HR 2,54 (95% IC : 1,32 – 4,87), p = 0,005]. A Metabolic Tumoral Volume (MTV) in the lymph nodes >2,2 mL was associated with worse PFS [HR 1,06 (95% IC : 1,03 – 1,10), p<0,001], using an MTV definition of voxels ≥ 45% of SUV Max. Finally, a higher cumulative distance between the barycenter of each metastasis and the barycenter of all metastases (d > 7,9 cm) was predictive for worse OS [HR 6,76 (95% IC : 2,39 – 19,16), p = 0,0003] and DMFS [HR 5,5 (95% IC : 2,16 – 14,01), p = 0,0004]. Conclusion Pre-therapeutic parameters extracted from PET/CT seem to be associated with prognosis in patients treated for non metastatic anal cancer treated with chemoradiotherapy. These results must be validated in an independent cohort. In association with other parameters, predictive models could allow us to better individualize the management of these patients. G. Chiloiro 1 , C. Di Dio 2 , D. Cusumano 2 , F. Catucci 2 , L. Boldrini 3 , A. Romano 3 , E. Meldolesi 3 , F. Marazzi 3 , B. Corvari 3 , B. Barbaro 4 , R. Manfredi 4 , V. Valentini 3 , M.A. Gambacorta 3 1 Fondazione Policlinico universitario A. Gemelli IRCCS, Radiation Oncology, Rome, Italy; 2 Mater Olbia Hospital, Radiation Oncology, Olbia, Italy; 3 Fondazione Policlinico universitario A. Gemelli IRCCS, Radiation Oncology, Roma, Italy; 4 Fondazione Policlinico universitario A. Gemelli IRCCS, Radiology, Roma, Italy Purpose or Objective Several studies have been conducted to evaluate the efficacy of adding of Oxaliplatin (OXA) to neoadjuvant chemoradiotherapy (nCRT) in patients with locally advanced rectal cancer (LARC), however the benefit remains unclear. Such as the 25% of patients develop metastases within five years after the end of surgery, a strategy to validate the role of nCRT intensification regimens in patients at higher risk of developing metastases should be investigated. Aim of this study is to create a radiomic model able to calculate the probability of 5-years Disease Free Survival (5yDFS) when OXA is or not administered in patients affected by LARC and nCRT, allowing physicians to choose the best chemotherapy (CT) regimen. Materials and Methods Patients with cT3-4 cN0 or cT1-4 cN1-2 rectal cancer were treated according to an nCRT protocol that included concomitant CT schedules with or without OXA and radiotherapy dose of 55 Gy in 25 fractions. Radiomic analysis was performed on the T2-weighted Magnetic Resonance (MR) images acquired during the initial tumor staging. Statistical analysis was performed separately for the cohort of patients treated with and without OXA, respectively. The ability of each single radiomic feature in predicting 5yDFS as a univariate analysis was assessed using the Wilcoxon Mann Whitney (WMW) test or t-test. Two logistic models (one for each cohort) were calculated, and their performance was assessed using the area under the Receiver Operating Characteristic (ROC) curve (AUC). A total of 176 image features belonging to four families (morphological, statistical, textural and fractal) were calculated for each patient. The clinical characteristics of the patients included in the study are summarised in Table 1. At univariate analysis the only feature showing significance in predicting 5yDFS was the maximum fractal dimension of the subpopulation identified considering 30% and 50% as threshold levels (maxFD 3050 ). Once the models were developed using this feature, an AUC of 0.67 (0.57-0.77) and 0.75 (0.56-0.95) was obtained for patients treated with and without OXA, respectively. A maxFD 30-50 >1.6 was correlated to an higher 5yDFS probability in patients treated with OXA. Figure 1 summarizes the values obtained in terms of 5yDFS probability when Oxaliplatin is or is not administered to varying of maxFD3050 values, applying the two models developed. Table1 PO-1327 Fractal-based radiomic approach to tailor the chemotherapy treatment in rectal cancer Results