Personalized oncogenomic analysis of metastatic squamous cell carcinoma of the anus: Utilizing whole-genome sequencing to guide clinical decision-making.

11 Background: Metastatic squamous cell carcinoma of the anus (SCCA) is associated with significant morbidity and mortality. Due to its relative rarity, there is limited evidence to support systemic therapy regimens informed by genomic data. This study aims to utilize whole-genome and transcriptome sequencing to enhance the understanding of the genetic alterations driving metastatic SCCA and to identify potentially actionable therapeutic targets. Methods: This report examines nine cases of metastatic SCCA in patients enrolled in the Personalized Oncogenomics (POG) Program at the BC Cancer Agency. Comprehensive genomic profiling, including whole-genome and transcriptome analysis (WGTA) was conducted on fresh tumor biopsy or formalin fixed paraffin embedded (FFPE) tissue. Tumor genomic alterations were analyzed in detail including: SNVs, indels, copy number alterations, structural variants, mutation signatures, viral presence, tumor mutation burden (TMB), expression outliers, and immune cell scores. The somatic alterations were integrated with existing knowledge of drug-target interactions to identify actionable therapeutic targets. Results: Of the nine patients, eight were found to be HPV-positive, with one exhibiting high tumor mutational burden (TMB>10mut/Mb). Mutation signatures included seven cases with AID/APOBEC signatures (commonly seen with HPV), and one case with an ID2 DNA replication slippage signature. The PI3K/AKT/mTOR pathway was the most commonly affected signaling pathway (n=4), followed by FGFR amplification and overexpression (n=3), and RAS/RAF alterations ( BRAF mutation and KRAS overexpression, n=2). EGFR amplification was identified in two cases, one of which also exhibited EGFR overexpression. Additionally, FBXW7 mutations were present in two cases. Immunotherapy was recommended for all nine patients: eight based on HPV positivity, either alone or in combination with other alterations, such as high TMB, SWI/SNF complex alterations, and presence of immune infiltrating cells, and the remaining case based on a SWI/SNF complex mutation. Only two patients ultimately received immunotherapy, both of whom derived clinical benefit. One patient, treated with atezolizumab as part of the phase II CAPTIV-8 trial (NCT04273061), demonstrated progression-free survival (PFS) of 10 months (ongoing), while the other, treated with nivolumab, achieved a PFS of 6 months. Conclusions: Genomic analysis using WGTA supported the recommendation of immunotherapy for all patients in this cohort. Although only two patients received immunotherapy, both experienced clinical benefit, underscoring the potential of personalized genomic-guided treatment in metastatic SCCA.