PROJECT SUMMARY/ABSTRACT Worldwide, cervical cancer (CxCa) is the 4th most common cancer in women. In the US, up to 60% of CxCa survivors will have persistent Human Papillomavirus (HPV), the causative agent of CxCa, and 35% will develop recurrent CxCa within 2 years of treatment. Microbes could influence outcomes through a wide variety of mechanisms, and the vaginal microbiome (VM) has been linked with persistent HPV and other infections, but the exact processes are poorly understood. Here we propose a secondary analysis to evaluate the changes over time of the VM and HPV strains in association with CxCa recurrence in CxCa survivors who have been followed up to 2 years after completing radiation therapy. Available stored samples collected from 80 participants will be used in this study: 40 postmenopausal CxCa patients who, and 40 healthy age- and race-matched controls. Vaginal swabs for microbiome sequencing, and cervicovaginal swabs for HPV genotyping have been collected at baseline before the initiation of cancer therapy, and at 3, 6 and 12 months post radiation therapy. We will obtain vaginal microbiome data via 16S rRNA sequencing as well as shotgun metagenomics in order to characterize the vaginal microbial communities. HPV typing of all available samples will be performed to identify the 51 most commonly encountered types. All subjects have been monitored for at least 2 years post-treatment, which is the mean time at which cervical cancer recurs. Association analysis will be performed to link the microbial community types with the HPV types and persistence, and cervical cancer recurrence. Understanding the role that the VM plays in persistent HPV infection and cancer recurrence can guide future interventional strategies such as probiotics, in order to effectively sustain a healthy vaginal microbiome that can protect against persistent infections in cancer survivors.