ESTRO 2023 - Abstract Book

S68

Saturday 13 May

ESTRO 2023

Sex

Male Female

45 (81.8) 10 (18.2)

ECOG PS 0 1

46 (83.7) 9 (16.3)

Primary Tumor Site Base of Tongue Tonsil Soft Palate Unknown Primary

31 (56.4) 22 (40) 1 (1.8) 1 (1.8) 1 (1.8) 31 (56.4) 23 (41.8) 6 (10.9) 49 (89.1) 14 (25.5)

T Category 0 1 2 N Category 0 1

Prior Malignancies Smoking History Never Former/Current

30 (54.5) 25 (45.5)

Conclusion Selection of personalized radiotherapy fractionation using the PSI model appears to be a promising approach, with an improvement in the percentage of patients achieving a mid-treatment imaging response compared to historical controls. Grade 3 acute toxicity was seen in 9.1% of patients, with no patients requiring a gastrostomy tube related to therapy. Initial PFS results with this approach appear favorable. OC-0107 Target and failure pattern in SCC-HNCUP: a prospective phase-4 study from DAHANCA S.B. Nielsen 1 , N.M. Lyhne 2 , M. Andersen 3 , J. Johansen 4 , C. Godballe 5 , H. Primdahl 6 , E. Andersen 7 , M. Farhadi 8 , A. Gothelf 9 , C.C. Plaschke 10 , T. Kjærgaard 11 , J. Overgaard 12 1 Aarhus University Hospital, Department of Experimental Clinical Oncology & Department of Otorhinolaryngology, Head and Neck Surgery, Aarhus, Denmark; 2 Aalborg University Hospital, Department of Otorhinolaryngology, Head & Neck Surgery and Audiology, 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 Herlev Hospital, Department of Oncology, Herlev, Denmark; 8 Zealand University Hospital, Department of Oncology, Næstved, Denmark; 9 Rigshospitalet, Department of Oncology, Copenhagen, Denmark; 10 Rigshospitalet, Department of Otorhinolaryngology, Head and Neck Surgery & Audiology, Copenhagen, Denmark; 11 Aarhus University Hospital, Department of Otorhinolaryngology, Head and Neck Surgery, Aarhus, Denmark; 12 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark Purpose or Objective The Danish national guidelines for head and neck squamous cell carcinoma of unknown primary (SCC-HNCUP) is from 2013. The guideline recommends bilateral elective neck irradiation. Elective mucosal areas typically include pharynx and larynx. Depending on affected neck node levels, nasopharynx is omitted in some cases and in other cases, only the oral cavity and oropharynx are irradiated. Trends towards a more individualized treatment approach with unilateral irradiation are emerging. Aiming to assess compliance to treatment guidelines, a comparative matching of radiation treatment (RT) plans with guidelines was performed. Regional failures were described in relation to planned CTV’s (unilateral/bilateral) to evaluate whether the recurrences occurred in prophylactic irradiated areas. Materials and Methods All patients who received RT as part of treatment for SCC-HNCUP in Denmark between 2014 and 2020 were included. Elective mucosal clinical target and elective nodal clinical target volumes from RT plans were obtained and compared with the topography of any ipsilateral or contralateral loco-regional failures. Results A total of 193 patients received curative radiotherapy as part of their treatment; 80 with primary (C)RT and 113 with adjuvant (C)RT. Concomitant chemotherapy was cisplatin (40 mg/m2 weekly). Seventy percent of patients treated with primary (C)RT received concurrent nimorazole. Patients were predominantly treated with IMRT (97%). A subfraction (17%) received elective neck irradiation unilaterally for unilateral neck disease. After a median (IQR) follow-up time of 3.1 (1.4 to 5.1) years, 10% had an in-field recurrence on the irradiated side of the neck. No patients treated unilaterally had a recurrence contralaterally. Seven percent had bilateral neck node disease. All of these were treated with bilateral RT, and 7% of these had regional in-field recurrence. Sixty-seven percent of mucosal failures occurred within the elective target volume. 5-year loco-regional failure rate was 19%. Conclusion We present the largest failure pattern analysis on a complete national cohort of SCC-HNCUP patients to date. Loco-regional failures are described in relation to planned CTVs. The loco-regional control was acceptable and comparable to primary head and neck SCC in other sites.