ESTRO 2024 - Abstract Book

S1393

Clinical - Head & neck

ESTRO 2024

1 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark. 2 Copenhagen University Hospital, Department of Oncology, Copenhagen, Denmark. 3 Aarhus University Hospital, Department of Pathology, Aarhus, Denmark

Purpose/Objective:

Distant metastasis (DM) significantly impacts the prognosis of patients diagnosed with head and neck squamous cell carcinoma (HNSCC). The accurate diagnosis of DM is challenged by the differential diagnosis of secondary primary tumors (SPT), especially in the lung, as both HNSCC and primary lung SCC are associated with smoking. The distinction has significant implications for treatment decisions, prognosis, and correct evaluation of outcomes in registries and trials. Currently, there is a lack of established methods for distinguishing true HNSCC metastases from SPTs. We propose a novel gene-expression profile based on 22 genes, including frequently mutated genes in HNSCC, determined through next-generation sequencing (NGS). By analyzing mutational patterns and human papillomavirus (HPV) status, we evaluated the likelihood of a molecular relationship between HNSCC primaries and their corresponding lesions, including non-pulmonary sites. Patients were retrospectively identified from the Danish Head and Neck Cancer Database (DAHANCA), a database with prospectively recorded clinical data. Clinical characteristics and outcome information were acquired from DAHANCA. Inclusion criteria were pharyngeal and laryngeal squamous cell carcinoma (SCC) with entry at the department in question from 2007-2017, and development of distant metastatic disease at diagnosis (M1) or after primary treatment (DM). The availability of formalin-fixed, paraffin-embedded (FFPE) tissue from both primary tumors and corresponding metastases was identified in the Danish Pathology Register, together labeled as a tissue block pair. Tissue block pairs were requested from pathology departments and were successfully obtained from 55 patients. Each tissue block was cut for H&E staining, p16 staining, and total RNA/DNA extraction. H&E staining ensured tumor contents, while p16 immunohistochemistry or HPV-typing through NGS confirmed HPV positivity. Following DNA isolation from FFPE tumor samples, a cancer-gene targeted sequencing of 22 genes, included in the Ion AmpliSeq Colon and Lung Cancer Research Panel v2, was performed using the Ion Torrent S5 platform (Thermo Fisher Scientific). Targeted genes include the most frequently mutated genes in HNSCC, including TP53, PIK3CA, EGFR, and FGFR3. Library preparation, amplification, and sequencing were performed according to the manufacturer’s instructions. The Ion Reporter software version 5.6 (Thermo Fisher Scientific) was used for variant calling. In addition, p16-positive oropharyngeal carcinomas were analyzed for HPV subtypes using a custom designed HPV-specific primer panel covering all 25 carcinogenic, probably carcinogenic, or possibly carcinogenic HPV genotypes. Based on mutational pattern and HPV status and -type, we assessed whether tissue block pairs were likely to be molecularly related. Most frequently, the call was made based on similar TP53 variants, which are highly unlikely to be coincidental. Material/Methods:

Results:

Of 55 available tissue block pairs, 22 had too poor quality for analysis. In the final cohort of 33 patients, the majority had HPV-negative disease (See Table 1). Seven had M1 disease and 26 developed DM. Most were treated with radiotherapy with radical intent (76 %). The biopsies were from lung (N = 18), liver (N = 6), bone (N = 5), lymph nodes