S608
Clinical – Head & neck
ESTRO 2026
treatment-related toxicity. References:
to evaluate the impact of 68Ga-DOTATOC PET/MRI on treatment planning for image-guided SRS for patients
Sandow L, Thawani R, Kim MS, Heinrich MC. Paraganglioma of the Head and Neck: A Review. Endocr Pract. 2023;29(2):141-7. Keywords: Stereotactic Radiotherapy, HNO Paraganglioma Digital Poster 2938 Treatment Outcomes and Survival Impact of Clinical Stage and TreatmentModality in Hypopharyngeal Cancer Patients Po-Ju Lin 1 , Wen-Yi Wang 2 , Jin-Ching Lin 3 1 Department of Radiation Oncology, Chang Bing Show Chwan Memorial Hospital, Changhua, Taiwan. 2 Department of Nursing, Hung Kuang University, Taichung, Taiwan. 3 Department of Radiation Oncology, Changhua Christian Hospital, Changhua, Taiwan Purpose/Objective: To investigate treatment outcomes as well as survival impacts of clinical stage and differenttreatment modality in hypopharyngeal cancer (HPC) patients. Material/Methods: A total of 155 newly diagnosed HPC patients without distant metastasis who received organ-preserving treatment were retrospectively reviewed. There were 154 males and one female, medianage=54 (range 32- 76), pretreatment performance status ECOG 0/1/2=14/123/18; overall stageII/III/IVa/IVb=4/21/102/28. All patients were squamous cell carcinoma. We divided treatmentmodality into CC and IC subgroups. CC groups included concurrent chemoradiotherapy (CCRT)for 62 patients and cetuximab-RT for 4 patients. IC group consisted of induction chemotherapy withcisplatin, 5-FU with/without docetaxel for 89 cases, followed by RT (n=27), CCRT (n=42), andcetuximab-RT (n=20). Results: After a median follow-up of 79 months, we observed 76 treatment failures, 89 deaths, and 24second primary cancers. The 5-year local failure-free survival (LFFS), regional failure-free survival(RFFS), distant failure-free survival (DFFS), relapse-free survival (RFS) and overall survival (OS)rates were 62.8%, 66.0%, 76.4%, 48.9%, and 43.6%, respectively for the whole cohort. IC groupcompared with CC group did not improved any survivals. Patients with stage II/III compared withstage IV had better survivals (LFFS P=0.0961, RFFS P=0.0452, DFFS P=0.1536, RFS P=0.0204,and OS P=0.2376). Conclusion: There is still room for improvement using non-surgical treatment for HPC patients. Development ofsecond
with paraganglioma. Material/Methods:
We retrospectively searched for patients with head and neck paragangliomas who underwent 68Ga- DOTATOC PET/MRI as part of clinical routine prior to SRS between 2022 and 2025. These same lesions were then independently re-contoured by a trainee radiation oncologist and subsequently validated by an experienced radiosurgeon, both of whom were blinded to the PET data and relied solely on MRI and CT images (GTVMRI). A 1-mm margin was added to generate the corresponding planning target volume (PTVMRI). The planning target volume used for the treatments, which was based on PET-guided delineation, served as the reference standard (PTVPET). Volume comparisons were performed using volume-based metrics, including overlap, left-out volume representing regions missed without PET, and excess volume representing regions delineated without PET but omitted when PET information was available. Furthermore, the Dice Similarity Coefficient (DSC) was computed. To assess the clinical impact of the different target definitions, coverage of each GTV was evaluated using the dose distribution of the applied treatment plan. Results: We identified a total of 10 patients (7 females and 3 males) aged between 64 and 74 years. In 9/10 cases, the MRI-based GTV was smaller with a median overlap between both volumes of 72.8% [IQR: 72.1%-82.2%] (DSC: 0.83 [IQR: 0.80-0.86]). The median left-out volume was 27.3% [IQR: 17.8%-27.9%], while the median excess volume was 8.6% [IQR: 8.0%-9.9%]. Based on the original treatment plan, the median dose coverage was 93.4% [IQR: 88.4%-95.6%] for the MRI- based GTV compared to 99.3% [IQR: 96.8%-99.7%] for the PET-guided GTV, reflecting the impact of target definition changes when PET imaging is not incorporated. Conclusion: Although the overall Dice coefficient indicated good agreement, MRI-only GTVs were smaller in the majority of patients. 68Ga-DOTATOC PET/MRI has the potential to enhance tumor delineation and minimize the risk of geographic miss, thereby improving treatment precision. Prospective studies are warranted to validate its impact on local control and
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