ESTRO 2022 - Abstract Book

S914

Abstract book

ESTRO 2022

13.7 months from 16.5 to 25 months, every 33.5 months from 25 to 99 months. Regarding surveillance of distant events, the optimal follow-up intervals were much longer: for HPC/LC/NPC, every 5.6/7.8/12.5 months until 27.5 months after treatment, every 15.9/22.0/35.4 months from 27.5 to 99 months and open follow-up thereafter; for HPV- OPC/HPV+ OPC, every 6.6/18.8 months until 27.5 months after treatment, every 18.8/53.2 months from 27.5 to 99 months and open follow- up thereafter. The proposed schedule could save an average of 11 outpatient visits and 1,481,590 won per person compared to the previous routine schedule. Conclusion The optimal assessment schedule for HNC layered by subsites and HPV status can be reasonably determined using parametric modeling of EFS. Due to the limited healthcare resource and an increasing number of HNC patients, this evidence-based assessment model will be worthwhile.

PO-1080 Dosimetric Evaluation of Risk of Osteoradionecrosis (DERO): setting-up and first results.

M. Renouf 1 , G. Delpon 2 , E. Bardet 1 , M. Doré 1

1 Institut de Cancérologie de l'Ouest René Gauducheau, Radiation Oncology, Nantes, France; 2 Institut de Cancérologie de l'Ouest René Gauducheau, Radiation Physics, Nantes, France Purpose or Objective OsteoRadioNecrosis (ORN) is a late complication of radiation for head and neck cancer which can lead to severe sequelae. Predicting ORN is a major challenge. We developed DERO (Dosimetric Evaluation of Risk of ORN), a semi-automatic dosimetric tool which reports doses delivered to tooth-bearing sectors, in a quick and reproducible way. We present the first results. Materials and Methods Dosimetric data of patients treated by IMRT for head and neck cancer were prospectively submitted to the DERO algorithm. 4 arches corresponding to each 8-tooth sector were semi-automatically generated. 32 cylindrical Regions Of Interest (ROI) corresponding to each tooth and surrounding periodontium were created by linear interpolation. Mean doses (Dmean) of ROI were extracted and included in a data base, along with data about diagnosis, laterality and dose values from organs at risk such as mandible. We focused on mandibular sectors: average Dmean to tooth sectors were grouped into molar sectors (teeth 5 to 8) and anterior sectors (teeth 1 to 4). An individual dose map was generated and delivered to patients and dentists (Fig 1).

Fig. 1. Example of individual dose map generated with DERO

Results Dosimetric data from 125 patients treated for head and neck cancer with Tomotherapy® were prospectively collected and analyzed: 9 parotid tumors (PA), 41 Sub-Hyoid tumors (larynx, hypopharynx) (SH), 43 Oropharynx tumors (OR), 32 Oral Cavity tumors (OC). Irradiation was unilateral for 100% of PA tumors (9), 12% of OR tumors (5) and 47% of OC tumors (15). All SH tumors were treated with bilateral radiation. For unilateral cervical irradiation, average Dmean in ipsilateral molar sectors was 54 Gy for OC tumors, 45 Gy for OR tumors, 20 Gy for PA tumors. For Oral Cavity bilateral irradiation, Dmean was high in all tooth sectors, 49 to 55 Gy. For SH tumors, Dmean in molar sectors was 27 Gy. A dose gradient of 10 up to 20 Gy was observed between molar and anterior sectors whether radiation was uni or bilateral.

Conclusion