ESTRO 2022 - Abstract Book

S377

Abstract book

ESTRO 2022

Conclusion The PPV for PET-CT at 12 weeks is lower for patients who have HPV-positive disease and for those who received CRT, especially amongst those who achieved an EQR. Additional biomarkers are needed to help select patients for further surveillance or ND.

OC-0434 Unknown Primary Head and Neck SCC: a phase-4 population-based cohort study from DAHANCA

S.B. Nielsen 1 , N.M. Lyhne 2 , M. Andersen 3 , J. Johansen 4 , C. Godballe 5 , H. Primdahl 6 , T. Kjærgaard 7 , J. Overgaard 8

1 Aarhus University Hospital, Department of Otorhinolaryngology, Head and Neck Surgery and Experimental Clinical Oncology, Aalborg, Denmark; 2 Aalborg University Hospital, Department of Otorhinolaryngology, Head and Neck Surgery, Aalborg, Denmark; 3 Aalborg University Hospital, Department of Oncology, Aalborg, Denmark; 4 Odense University Hospital, Department of Oncology, Odense, Denmark; 5 Odense University Hospital, Department of Otorhinolaryngology, Head and Neck Surgery and Audiology, Odense, Denmark; 6 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 7 Aarhus University Hospital, Department of Otorhinolaryngology, Head and Neck Surgery, Aarhus, Denmark; 8 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark Purpose or Objective Management of patients with squamous cell carcinoma metastasis of an unknown primary in the head and neck (SCC-HNCUP) remains a challenge. In Denmark, the diagnostic work-up and treatment of SCC-HNCUP is standardized and follow national guidelines provided by the DAHANCA group. However, international consensus regarding treatment strategy is lacking and so is knowledge about treatment outcome. The clinical radiotherapy (RT) target for SCC-HNCUP according to current DAHANCA guidelines involves bilateral regional lymph nodes and potential mucosal primary tumor sites. Neck dissection (ND) alone is recommended in N1-disease (UICC 7). The aim of the current study is to evaluate the oncologic outcome in patients with SCC-HNCUP treated according to the Danish national guidelines. Materials and Methods Prospectively registered data was extracted from the DAHANCA database. All patients treated for SCC-HNCUP at Aalborg, Aarhus and Odense University Hospitals in the period 2014-2020 were included. The median follow-up was 35 months (IQR 44 months). Results A total of 177 patients were identified. 153 (86%) patients received curatively intended treatment with surgery, RT and chemotherapy, either alone or in combination. Twenty (11%) patients received palliative treatment. Four patients underwent no treatment. Sixty-one (34%) patients were treated with curatively intended RT alone, 54 (31%) received CRT with concomitant weekly cisplatin 40 mg/m 2 . Fourteen patients received accelerated RT with 6 fractions per week