Abstract B091: Vulvar squamous cell carcinoma: Comprehensive genomic profiling of HPV(+) versus HPV(–) forms reveals a different set of potentially actionable biomarkers

Introduction: One major form of vulvar squamous cell carcinoma (vSCC) is associated with detectable high-risk strains of human papillomavirus (hrHPV) and is often accompanied by usual-type vulvar intraepithelial neoplasia (VIN). The second major form of vSCC is often associated with chronic dystrophic or inflammatory lesions in postmenopausal women, does not harbor detectable HPV infection, and is often preceded by p53-mutant differentiated VIN. While studies have examined the two subtypes, no large-scale genomic study has been performed to our knowledge. We sought to assess the genomics of a large cohort of aggressive vSCCs, with an aim to identify distinct mutational signatures based on the presence or absence of hrHPV genome reads. Methods: 280 vSCC were tested by hybridization capture of up to 406 cancer-related genes evaluated for base substitutions, small indels, amplification (amp), and rearrangements. HPV genome sequences were detected by de novo assembly of non-human sequencing reads and BLASTn comparison against all viral nucleotide sequences in the NCBI RefSeq database. Tumor mutational burden (TMB, mutations/Mb) was determined on ~1.1 Mbp of sequenced DNA. PD-L1 status was determined by IHC (Dako 22C3), with ≥50% tumor proportion score defined as high positive. Results: 102/280 vSCCs contained hrHPV sequences. Of these, 90 were HPV-16, 7 HPV-18, 1 HPV-31, 3 HPV-33, 1 HPV-58, and 1 HPV-67. Patients were significantly younger in the HPV(+) group (median 59 v. 64 years, p=0.001). Compared with the HPV(–) cohort, HPV(+) cases showed significantly more pathogenic genomic alterations (GA) in PIK3CA (31% vs. 17%, p=0.004), PTEN (14% vs. 2%, p10*6%24%3%19% Conclusions: vSCCs show significant differences in molecular profile based on HPV status. 63% of metastatic HPV(+) cases (54% overall) have a potentially actionable alteration in the PI3K/mTOR pathway, and 42% of metastatic HPV(–) cases (39% overall) have at least one potential predictive biomarker* for response to immunotherapy. Our findings provide compelling rationale for tandem comprehensive genomic profiling and HPV assessment of advanced vulvar SCCs to more fully inform therapeutic options and stratification in clinical trials. Citation Format: Erik A Williams, Adrienne J Werth, Meagan Montesion, Ethan S Sokol, Dean C Pavlick, Nikunj A Shah, Jo-Anne Vergilio, Natalie A Danziger, Jonathan K Killian, Douglas A Lin, Vincent A Miller, Jeffrey S Ross, Julia A Elvin. Vulvar squamous cell carcinoma: Comprehensive genomic profiling of HPV(+) versus HPV(–) forms reveals a different set of potentially actionable biomarkers [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B091. doi:10.1158/1535-7163.TARG-19-B091