ESTRO 2021 Abstract Book

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ESTRO 2021

[1] Sanguineti (2009) Int. J. Rad. Onc. Biol. Phys. 74 (5) 1356–1364

Results Figure 2 shows the risk of occult metastases in LNL III and IV depending on T-stage and whether the upstream LNLs II and III harbor macroscopic metastases. For early T-stage, the expected risk for microscopic involvement of LNL III rises from 4.8 ± 1.0 % for N0 patients to 10.2 ± 1.8 % when macroscopic metastases in LNL II are observed. For late T-stage and macroscopic metastases in LNL II, the risk increases further to 13.7 ± 2.8 % (Figure 2 top). Analogous findings are observed for level IV (Figure 2 bottom). Figure 2

Conclusion HMMs provide a statistical framework to model the spread of lymphatic metastases. It allows us to estimate the risk of microscopic involvement of LNLs depending on T-stage and location of macroscopic metastases. But larger datasets of detailed involvement patterns, rather than reports of only prevalence, are needed before the model may inform guidelines for CTV-N definition. Acknowledgement: This work was supported by the Clinical Research Priority Program Artificial Intelligence in Oncological Imaging of the University of Zurich. PH-0108 New dose-volume constraints for patient-reported acute bowel toxicity symptoms in whole pelvis IMRT A. Bresolin 1 , A. Faiella 2 , E. Garibaldi 3 , F. Munoz 4 , D. Cante 5 , V. Vavassori 6 , J.M. Waskiewicz 7 , G. Girellli 8 , B. Avuzzi 9 , E. Villa 6 , A. Magli 10 , B. Noris Chiorda 9 , M. Gatti 3 , L. Ferella 4 , A. Maggio 11 , V. Landoni 12 , S. Aimonetto 13 , C. Sini 1 , T. Rancati 14 , G. Sanguineti 2 , R. Valdagni 9 , N. Di Muzio 15 , C. Cozzarini 15 , C. Fiorino 1 1 San Raffaele Scientific Institute, Medical Physics, Milan, Italy; 2 IRCCS Istituto Nazionale dei Tumori Regina