Background: Penile cancer is a rare disease associated with HPV infection and harbors recurrent somatic genomic alterations in the ERBB (HER)-family, CDKN2A, TP53, NOTCH1 and PIK3CA. ctDNA assay allows the noninvasive genomic profiling of malignancies and may assist with understanding molecular evolution. To our knowledge, the genomic alterations observed in ctDNA for penile cancer have not been described before. We report ctDNA profiling of patients with advanced penile cancer. Methods: Sixteen pts with metastatic penile cancer from multiple institutions in the United States that underwent ctDNA analysis using the Guardant360 platform were eligible. Three patients had at least one serial ctDNA sample. De-identified demographic data were collected. Guardant 360 is CLIA-certified ctDNA panel that assesses single nucleotide variants and copy number alterations in 68 to 73 genes for potentially actionable genomic alterations. Variants seen at least 3 times in the Catalogue of Somatic Mutations in Cancer (COSMIC) database or reported in OncoKB were considered pathogenic. Results: The median age was 64 years (range 40-77). 4 pts (25%) were documented to be post platinum-based chemotherapy. Among the entire cohort, 51 ctDNA alterations were detected (median=2, range 0-6) in 15/16 patients (94%) across 21 genes (table). Of the 51 alterations, 24 (47%) were actionable and had approved targeted therapies in other cancers. Alterations were most frequently detected in TP53 (9/16, 56%), CDKN2A (5/16, 31%), and TERT promoter (5/16, 31%) (table). In 3 patients with serial samples, 9 novel pathogenic alterations were detected in the second sample including ATM, CDKN2A, ARID1A, CCND1, CDK6, EGFR, PDGFRA, PIK3CA, and SMAD4. Conclusions: ctDNA alterations in patients with advanced penile cancer were frequently detected and appeared similar to previously described tumor tissue analyses. New alterations found on serial ctDNA assays shed light on patterns of tumor evolution and may inform drug development for this challenging orphan malignancy.