ESTRO 2022 - Abstract Book

S378

Abstract book

ESTRO 2022

(66Gy/33fx/5 ½ weeks) and 108 patients received conventional RT with 5 fractions per week (66 Gy/33fx/6 ½ weeks). Forty- six patients treated curatively with RT/CRT concurrently received nimorazole. Forty and 25 patients had a ND prior to RT and CRT, respectively. Thirty-five patients received ND as only curative modality. Neck node p16 status was unknown in 21 patients, negative in 78 patients and positive in 78 patients. Two patients had EBV-positive neck nodes. A primary tumor or secondary cancer emerged in the head and neck region in 17 patients during follow-up. Three tumors emerged in the hypopharynx, three in oral cavity and 11 in the oropharynx, of which 6 involved base of tongue. Time to loco-regional failure varied between 2 and 62 months. In three patients, a possible primary tumor emerged outside the head and neck area (1 esophagus, 2 lung). The 3-year OS for the total population was 72.8% (95% CI: 65.1, 79.1). For patients treated with curative intend, the OS at 3-years was 81.1% (73.4, 86.8). Three-year OS in patients with p16 positive disease treated curatively was 92.2% (82.1, 96.7), while patients with p16-negative and unknown p16 status had OS of 73.0% (60.5, 82.1) and 69.3% (31.2, 89.1), respectively. Conclusion Our data support that SCC-HNCUP is comparable to other head and neck cancers in terms of prognosis. Thorough multidisciplinary work-up is important in order to plan optimal curative treatment strategies for these patients.

OC-0435 Loco-regional failure is associated with the stem cell marker SLC3A2, volume and HPV/p16 in HNSCC

M.H. Kristensen 1 , B.S. Sørensen 1 , J. Alsner 1 , C.R. Hansen 2 , R. Zukauskaite 2 , E.S. Hinsby 3 , C. Maare 4 , J. Johansen 2 , H. Primdahl 5 , C.A. Christensen 6 , M. Andersen 7 , J. Lilja-Fischer 1 , T. Tramm 1 , J. Overgaard 1 , J.G. Eriksen 1 1 Aarhus University Hospital, Dept of Experimental Clinical Oncology, Aarhus, Denmark; 2 Odense University Hospital, Dept of Oncology, Odense, Denmark; 3 Zealand University Hospital, Dept of Oncology, Næstved, Denmark; 4 Herlev Hospital, Dept of Oncology, Herlev, Denmark; 5 Aarhus University Hospital, Dept of Oncology, Aarhus, Denmark; 6 Copenhagen University Hospital, Dept of Oncology, Copenhagen, Denmark; 7 Aalborg University Hospital, Dept of Oncology, Aalborg, Denmark Purpose or Objective Large tumor volume and HPV/p16- status are known to be poor prognostic factors for loco-regional failure for Head and Neck Squamous Cell Carcinoma (HNSCC) after primary curative radiotherapy (RT). However, the response to RT is heterogeneous and the objective was to identify the presence and possible impact of the stem cell marker SLC3A2. Materials and Methods Patients (Pts) in the study represented a subgroup of the DAHANCA 19 study with available formalin-fixed paraffin embedded (FFPE) primary tumor tissue. Pts were treated with primary RT 66-68Gy, 33-34fx, 6 fx/wk; concomitant weekly cisplatin (40mg/m 2 ) if UICC stage III/IV (7 th ed.) and the hypoxic radiosensitizer nimorazole. FFPE tumor tissue were collected and dissected and sufficient amount of cancer tissue was ensured. RNA was extracted and qPCR was applied to measure the gene expression of the cancer stem cell marker SLC3A2. Selected reference genes were used to determine the relative expression of SLC3A2. Volume of GTV-T and -N (GTVTot) was extracted from the original planning-CT. p16-status was evaluated with immunohistochemistry with a cut-off of 70 %. SLC3A2 was categorized according to expression and p16 status. Further subclassification was performed according to HPV/p16-status, 50-percentile of SLC3A2 (high/low) and GTVTot (large/small) into three predefined groups. Loco-regional failure was used as endpoint and Cox-regression was used to establish hazard ratios (HR). Results Full data-sets were available from 143 primary tumors. Primary tumor site was: oral cavity ( n =4); oropharynx ( n =114; of those were 72 p16 positive); larynx ( n =25). Expression of SLC3A2 was more prominent in HPV/p16 negative tumors compared to HPV/p16 positive tumors, p<0.001 (Fig. 1). When dividing pts into the three predefined groups, the risk of loco-regional failure was significantly worse for tumors with large volume, HPV/p16 negative status and high SLC3A2 compared to tumors with low volume, HPV/p16 positivity and low SLC3A2, p<0.001 (Fig. 2). In total, 4 % of the pts in the low risk-group ( n =27) and 56 % in the high-risk group ( n =26) had loco-regional failure. In a multivariate Cox-regression the above mentioned classification was the most important factor (HR=0.07; 95%CI(0.007- 0.6); p =0.02) among stage, T-stage, nodal status, tumor differentiation grade and tumor site.