ESTRO 2022 - Abstract Book

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Abstract book

ESTRO 2022

Conclusion SMART for rectal cancer is well tolerated and effective in terms of tumor regression. This radiation treatment can help to achieve a complete pathological response in selected patients, especially when followed by delayed surgery. In addition, short-course schedule is less expensive and time saving, therefore SMART could be useful to treat a larger number of patients and to reduce patients’ waiting list. However, further studies are required to confirm these findings.

PD-0496 Downstaging as an early predictor in rectal cancer: results of a pooled dataset of 4167 patients

G. Chiloiro 1 , M. Savino 2 , A. Romano 3 , C. Masciocchi 3 , J. Van Soest 4 , J. Gérard 5 , S.Y. Ngan 6 , C. Rödel 7 , A. Sainato 8 , A. Damiani 3 , A. Dekker 4 , M.A. Gambacorta 3 , V. Valentini 3 1 Fondazione Policlinico Universitario A. Gemelli IRCCS, Radiation Oncology, Roma, Italy; 2 Università Cattolica del Sacro Cuore, Radiation Oncology, Rome, Italy; 3 Fondazione Policlinico Universitario A. Gemelli IRCCS, Radiation Oncology, Rome, Italy; 4 University Medical Centre, Radiation Oncology - MAASTRO, Maastricht, The Netherlands; 5 Centre Antoine- Lacassagne, Radiation Oncology, Nice, France; 6 Peter MacCallum Cancer Centre, Radiation Oncology, Melbourne, Australia; 7 University of Frankfurt, Radiation Oncology, Frankfurt, Germany; 8 Pisa University Hospital, Radiation Oncology, Pisa, Italy Purpose or Objective Downstaging in locally advanced rectal cancer (LARC) undergoing neoadjuvant chemoradiation (nCRT) treatment is defined as a decrease in pathological vs preoperative T-category, N-category, or disease stage. Several studies have shown that downstaging is a potential early predictor of nCRT efficacy. The proper definition of downstaging and its impact on survival outcomes remain to be defined. The aim of this analysis is to evaluate the impact of downstaging on survival outcomes in a pooled dataset of several randomized trials of neoadjuvant radiotherapy in LARC. Materials and Methods Pooled and treatment subgroup analysis were performed on 8 large international rectal cancer trials: Accord 12/0405, EORTC 22921, FFCD 9203, CAO/ARO/AIO-94, CAO-ARO-AIO-04, INTERACT, I-CNR-RT, and TROG 01.04. All selected patients were older than 18 years, had undergone nCRT with or without adjuvant chemotherapy (CT) followed by surgery, and with information on at least one among T-, N-, or stage downstaging. Metastatic patients or those who underwent conservative surgery, such as minimally invasive transanal excision (TAMIS) or transanal endoscopic microsurgery (TEM), were excluded from the analysis. Overall survival at 5 years (5yOS), distant metastasis free survival at 2 years (2yDMFS) and disease free survival at 2 years (2yDFS) rates were calculated using Kaplan Meier analysis. Patients were defined as downstaged when the difference of clinical and pathological stages (respectively on T value, N value and the TNM stage) was greater than or equal to 1. Kaplan Meier curve, Logrank test and univariate logistic regression were used for data analysis. A p-value less than 0.01 was considered as a statistical significant value.

Results