ESTRO 2023 - Abstract Book

S966

Digital Posters

ESTRO 2023

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Conclusion Intensity-modulated radiation therapy may provide good local and overall disease control without severe toxicity for differentiated thyroid cancer patients with inoperable/unresectable locoregional recurrence. Radiotherapy may be offered to patients who would like to defer oral tyrosine kinase inhibitors to avoid systemic toxicities. Our data may serve as a reference for discussion with patients for shared decision-making.

PO-1208 Is bilateral RT necessary for patients with unilateral SCC-CUP of the head and neck region?

L. Oebel 1 , A. Mayer 1 , J. Kaufmann 1 , D. Wollschläger 2 , J. Hagemann 3 , M. Krüger 4 , H. Schmidberger 1

1 University Medical Center Mainz, Radiation Oncology, Mainz, Germany; 2 University Medical Center Mainz, Institute of Medical Biostatistics, Epidemiology and Informatics (IMBEI), Mainz, Germany; 3 University Medical Center Mainz, Head and Neck Surgery, Mainz, Germany; 4 University Medical Center Mainz, Oral and Maxillofacial Surgery, Mainz, Germany Purpose or Objective In squamous cell carcinoma of unknown primary (CUP) of the head and neck region, it is unclear whether contralateral irradiation of the cervical lymph node levels is necessary in case of unilateral involvement. This question is of relevance both for possible locoregional recurrences and the development of distant metastases. Materials and Methods 50 patients with unilateral SCC CUP syndrome of the head and neck region who received radiotherapy at the Department of Radiation Oncology, University Medical Center Mainz, from 2005 to 2019 were evaluated based on patient records. 30 patients received bilateral radiotherapy, and the remaining 20 received unilateral radiotherapy. The decision for unilateral or bilateral therapy rested with the responsible physician and did not follow a predefined protocol. Of the 50 patients, the majority received adjuvant irradiation (39 patients), and a minority (11 patients) received primary (chemo)radiotherapy. Recurrence patterns were analyzed relative to the dose distribution of radiotherapy using the Varian Eclipse planning system Version 16.1. Results No systematic differences in tumor stages are demonstrated between the unilateral and bilateral irradiation groups. After a median follow-up time of 64.5 months, locoregional recurrences occurred in 26 percent of cases (n=13/50). All locoregional recurrences occurred ipsilaterally, and predominantly in the high-dose volume (85%, n=11/13) of the previous irradiation. Only two recurrences occurred outside the irradiation target volume. Distant metastases (18% of cases, n=9/50) occurred more frequently in the bilaterally irradiated group (23% of cases, n=7/30) than in the unilaterally irradiated group (10% of cases, n=2/20). Overall locoregional control at 5 years was 66.2% in the bilaterally irradiated group and 70.0% in the unilaterally irradiated group, overall survival was only 52.6% (bilateral) and 64.0% (unilateral) in the groups, respectively. Distant metastasis-free overall survival was 74.7% (bilateral) and 84.4% (unilateral). Conclusion These data indicate that contralateral cervical irradiation is of limited benefit because recurrences occur primarily in the high-dose area of prior irradiation and patients' subsequent clinical outcome is dominated by the occurrence of distant metastases. However, unilateral irradiation undoubtedly reduces therapy-associated toxicity for those patients who remain without tumor recurrence in the longer term. To further increase the safety of therapy, FDG-PET/CT is recommended. J. Daisne 1,2 , S. Deheneffe 3 , T. Dragan 4 , F. Duprez 5 , H. Bollen 1 , S. Nuyts 1,2 , M. Martens 6 , A. Vancleef 7 , A. Maes 8 , M. Govers 8 , D. Van Gestel 4 , C. Bruyninckx 1 1 University Hospitals Leuven, Radiation Oncology, Leuven, Belgium; 2 Leuven Kanker Instituut, Oncology, Leuven, Belgium; 3 CHU-UCL-Namur (site Ste-Elisabeth), Radiation Oncology, Namur, Belgium; 4 Institut Jules Bordet, Université Libre de Bruxelles, Radiation Oncology (Head and Neck Unit), Brussels, Belgium; 5 University Hospital Gent, Radiation Oncology, Gent, Belgium; 6 AZ Turnhout, Radiation Oncology, Turnhout, Belgium; 7 Onze Lieve Vrouw Hospital, Radiation Oncology, PO-1209 Sentinel lymph nodes identification with SPECT/CT for HNSCC radiotherapy: a multicentric dummy run