Squamous cell carcinoma of the oropharynx (SCCOP) is characterized by local tumor aggressiveness requiring morbid local-regional therapies with poor survival and high recurrence rates. Despite declining smoking prevalence, the incidence of SCCOP is increasing, particularly in young adults. These trends may be due to the rising prevalence of oncogenic human papillomavirus (HPV) in the population. HPV-positive [(HPV+)] SCCOP is a distinct epidemiologic, clinical, and molecular disease with potentially unique clinical behavior and treatment responses. Identification of those needing treatment intensification and those able to benefit from reduction of treatment intensity is critical to moreeffective and less morbid treatment. Oncogenic subtypes of HPV are critical etiologic factors in a distinct subset of head and neck cancers, chiefly SCCOP. Inflammatory response miRNAs which control the HPV clearance and escape of immune surveillance may contribute to HPV(+) tumors and related outcomes of SCCOP. In addition, miRNAs in human serum hold a great potential for serum-based biomarker research. Thus, serum expression profiles of inflammatory response miRNAs before treatment may affect tumor HPV status and related outcomes of SCCOP patients; and exploitation of such associations may help develop clinically relevant non-tumor-based biomarkers for HPV- associated SCCOP patients. In this study, the study subjects will be 600 patients with incident SCCOP identified from an existing molecular epidemiologic study of squamous cell carcinoma of the head and neck. The specific aims for this R03 project are: Aim 1: To assess if serum expression profiles of selected inflammatory/immune response miRNAs before treatment are markers of tumor HPV status among the 600 SCCOP patients. We will determine serum expression of those selected miRNAs before treatment by using the miScript miRNA PCR arrays method and Aim 2: To determine if certain serum expression profiles of above miRNAs before treatment as blood-based and non-tumor predictors of clinical outcomes of HPV(+) SCCOP patients including disease-specific survival, disease-free survival, and overall survival among 600 SCCOP patients treated and followed at U.T. MDACC. By knowing the tumor HPV status and identifying novel prognostic biomarkers of HPV-associated SCCOP patients, physicians can effectively tailor treatment, screening, and follow-up strategies for an improved survival and a better quality of life as well as greatly enhanced secondary cancer prevention.