ESTRO 2020 Abstract book

S1055 ESTRO 2020

competency and performance metrics required to establish and demonstrate mastery over these domains were developed for each member of the team. Results Detailed curriculum and evaluation quizzes have been developed to teach and assess basic knowledge. Case studies for various scenarios have been created for testing competence though written exams and discussions. Observations of simulated treatments with volunteer actors and realistic phantoms will be used to assess performance using. Ongoing audit of patient treatments is proposed to evaluate “action” of individuals and the team. Conclusion The framework provides a structured approach for educating and testing staff on new technologies and clinical procedures that are not formally learned during their initial training. PO‐1797 Dosimetric analysis of simultaneous integrated boost in the HYPORT Adjuvant Trial (NCT03788213) S. Bhusal 1 , S. Chatterjee 1 , S. Chakraborty 1 , A. Kumari 1 , S. Bachianathan 2 , A. Mahato 1 , P. Lal 3 , S. Gupta 4 , P. Solomon 2 , K.M. Das 3 , S. Mandal 1 1 Tata Medical Center, Radiation Oncology, Kolkata, India ; 2 Christian Medical College, Radiation Oncology, Vellore, India ; 3 Sanjay Gandhi Post Graduate Institute of Medical Sciences, Radiation Oncology, Lucknow, India ; 4 All India Institute of Medical Sciences, Radiation Oncology, Delhi, India Purpose or Objective The HYPORT adjuvant trial is a randomized trial comparing a one week (5 fractions) schedule of hypofractionated breast radiotherapy against a three week (15 fractions) schedule. As a part of this study, patients who have undergone breast conservation can undergo a Simultaneous Integrated Boost (SIB) to the boost cavity. Material and Methods The HYPORT Adjuvant is a multi-centric, open-label, phase III, parallel-group, two-arm randomized controlled trial. Patients requiring adjuvant radiotherapy after curative intent, margin negative, surgery are eligible. Patients were randomized to • Standard arm: 40 Gy in 15 fractions over 3 weeks to the whole breast +/- regional nodal RT • Experimental arm: 26 Gy in 5 fractions over 1 week to the same volumes. Patients undergoing BCS were eligible for SIB. A boost target volume (BTV) was generated around the tumor bed (marked with clips) by an isotropic expansion of 5 mm. A hybrid tangent beam whole breast radiation plan with a Volumetric Modulated Arc SIB (VMAT SIB) was used for SIB. The VMAT plan comprised of two coplanar 30-40 degree complementary arcs offset at an angle of 5 - 10 degree from the tangent. Doses of 8 Gy in 15 fractions and 6 Gy in 5 fractions is used for tumor bed boost in the standard and experimental arms, respectively. In the current study, we report adherence to the protocol and compare the dosimetry data between two arms. Results The trial opened for accrual on 28th March 2019 and 185 patients were enrolled in the study till September 2019. Sixty-four (34.6%) patients underwent BCS and of them, 58 (90%) patients received SIB.

Conclusion SIB plans in the standard and experimental arms of the HYPORT Adjuvant trial met the protocol defined constraints in all patients. The SIB strategy enabled the dosimetric sparing of the normal organs (especially contralateral lung, breast and heart) while ensuring conformity and homogeneity. PO‐1798 Quality of radiotherapy treatment plans for locally advanced sinonasal tumors in a phase II trial B. Vischioni 1 , A. Mirandola 2 , M. Bonora 1 , S. Ronchi 1 , E. Mastella 2 , E. Orlandi 3 , N.A. Iacovelli 3 , A. Cavallo 4 , L. Licitra 5 , C. Fallai 3 , M. Ciocca 2 , E. Pignoli 4 , S.M. Magrini 6 , P. Antognoni 7 , F. Valvo 1 1 Fondazione CNAO, Radiation Oncology Department, Pavia, Italy ; 2 Fondazione CNAO, Medical Physics Department, Pavia, Italy ; 3 Fondazione IRCCS Istituto Nazionale dei Tumori, Radiation Oncology 2, Milano, Italy ; 4 Fondazione IRCCS Istituto Nazionale dei Tumori, Medical Physics Unit, Milano, Italy ; 5 Fondazione IRCCS Istituto Nazionale dei Tumori, Head and Neck Medical Oncology Unit, Milano, Italy ; 6 Brescia University, Radiation Oncology Department, Brescia, Italy ; 7 Ospedale di Circolo e Fondazione Macchi, Department of Radiotherapy, Varese, Italy Purpose or Objective To investigate adherence to the quality assurance requirements for the treatment planning of the carbon ion (CI) boost phase for the patients (pts) enrolled in a multicentric trial for multimodal treatment of inoperable locally advanced sinonasal tumors. Material and Methods From 2013 to 2018, 25 pts with locally advanced unresectable sinonasal tumors of poor prognosis histology, were prospectively enrolled for multimodal treatment. 23/25 (2 withdrew consents) were treated with 3-5 cycles of neoadjuvant chemotherapy followed by modern radiotherapy technique (IMRT and/or particle therapy PT) with concomitant chemotherapy. Based on the results of an in silico phase of comparative treatment planning performed with IMRT or PT on the same patient computer tomography (CT), 14/23 pts received mixed-beam treatment of IMRT and CI, 7 received IMRT only, and 2 pts received full PT treatment. CI boost was performed on the High risk volume (PTV HIGH ) including the gross disease in 15 pts; in the majority of cases (14/15) the PTV HIGH was irradiated before IMRT, performed on the low risk volume (PTV LOW ) with elective neck, while in one case after CI phase. Median prescription dose of the CI boost was 15 Gy(RBE). Intensity modulated PT plans were calculated