Abstract BACKGROUND Correlative studies are common in early phase clinical trials. In addition to primary aims establishing maximum tolerated dose or efficacy, supplementary information from biospecimens is frequently collected with patient consent. The Pediatric Neuro-Oncology Consortium (PNOC) has included several correlative studies with implications for understanding patterns in the development of tumors, response to treatment, and prognosis. A needs assessment survey of PNOC institutions by the Advanced Practice Provider and Investigational Nurse Committee (APPNIC) highlighted that nurses and advanced practice providers (APPs) desire further education regarding correlative studies. METHODS Blood, stool, cerebrospinal fluid (CSF) and hair strands are examples of correlative biospecimens incorporated in PNOC protocols. We will share a review of the literature and implications for practice. RESULTS Blood, drawn in conjunction with clinical labs, is commonly analyzed for circulating tumor DNA to conduct molecular profiling in blood compared to tissue, explore less invasive means of molecular evolution of tumor somatic mutations, and identify early markers of tumor response or resistance. Stool is collected to utilize the gut microbiome as a lens into treatment response in CNS tumors via the gut-brain axis. Stool samples are compared to normal controls and longitudinally within patients during treatment. CSF sampling provides less invasive disease monitoring, tumor molecular characterization, markers of tumor response or resistance, and drug pharmacokinetics. Hair sampling can be used to further quantify drug levels for pharmacokinetics and assess treatment compliance. The robustness of these correlative samples collected at various timepoints (diagnosis, pre-surgery and post-surgery, post-radiation and/or with recurrence) informs on prognosis, response to treatment; and ultimately, interventions to improve outcomes for pediatric and young adult CNS tumors. CONCLUSION Our assessment identified a need for APP and nursing-focused education on biospecimen collection to inform on emerging clinical and research advances while improving protocol compliance.