e24122 Background: Neuroendocrine neoplasm (NEN) is a broad term that includes both neuroendocrine tumors (NETs) and neuroendocrine carcinomas (NECs). These rare malignancies most often occur in the gastrointestinal tract, pancreas, lung, adrenal medulla, and thyroid. Clinical symptoms depend upon several factors including tumor location, length of time since diagnosis, secretion of hormones, and tumor growth. Physical symptoms may include fatigue, gastrointestinal complaints, shortness of breath, and fluctuations in blood pressure, weight, and appetite. Patient reported outcomes (PROs) are critical in understanding the clinical spectrum of patients with NENs including their physical and social-emotional response to disease course and treatments. The aim of the current study was to assess physical, social, and emotional domains of PROs amongst a cohort of adult participants with NENs over time. Methods: Patients were enrolled on an ongoing NIH natural history study (NCT03739827). Annual PROs were electronically administered to adult participants (≥18 years) using the PRO Measurement Information System (PROMIS) forms for Anxiety, Depression, Fatigue, Mobility, Upper Extremity, Pain Interference, Cognitive Function, and Emotional Support ( www.nihpromis.org ). PROMIS forms are standardized on a T-Scale with a mean of 50 and a standard deviation of 10. Pain intensity was assessed from 0 (no pain) to 10 (worst pain imaginable) using the Numeric Rating Scale for Pain (NRS) (Wolters, 2013). The Pain Interference Index (PII) was used to assess the impact of pain on daily functioning on a 7-point Likert scale (Martin et al., 2015). Results: A total of 49 out of 85 patients provided completed PROs: 47 NET and 2 NEC. Mean (M) age was 58.8 years and 61.2% of the sample was female. Amongst NET patients (n = 47), primary tumor locations were the small bowel (45.7%), pancreas (21.7%), and lungs (13.0%). Other primary sites (19.6%) included the appendix, rectum, thyroid, kidney, and prostate. 46.8% had metastatic disease. Fatigue was the primary symptom complaint; 34% of NET patients reported fatigue in the moderate to severe range (Mean: 54.1; Standard Deviation: 11.2). Self-perceived mobility (M:47.4; SD: 9.1) and pain interference (M: 51.8; SD: 9.0) were a moderate concern for 19.1% and 17.0% of patients, respectively. At follow-up, 24 patients have returned PROs to date. Fatigue and mobility remained prevalent concerns; 29.1% of patients reported moderate to severe fatigue and 25% reported moderate concerns with mobility. Challenges with upper extremity mobility were endorsed by 20.8% of the sample. Conclusions: Our prospective and comprehensive PRO assessment confirms previously reported fatigue as the most prevalent symptom in patients with NET. Assessment of PROs over time will inform the development of clinical interventions and assessment of their impact on patient quality of life and functioning.