Background: In ELECT, LAN significantly reduced the need for short-acting OCT rescue medication for symptomatic control of CS in NET patients (pts) vs placebo (PBO) (primary result). Here we present flushing and diarrhea symptom data and biochemical response for pts with or without prior OCT use from the ELECT study. Methods: Adults with histopathologically confirmed NET and history of CS (diarrhea and/or flushing) who were OCT-naive or responsive to OCT long-acting release (LAR) (≤30 mg q4W) or short-acting OCT (≤600 μg daily) were randomized to LAN 120 mg (SC q4W) or PBO for 16 wks. Pts administered short-acting OCT if needed and recorded daily the frequency and severity of symptoms using Interactive Voice/Web Response System for 1 month pre-randomization and throughout the study. 24 hr urinary 5-hydroxindoleacetic acid (5HIAA) was assessed at baseline and wk 12. Results: Of 115 pts randomized, 51 (n=26 LAN; n=25 PBO) were OCT-naive and 64 (n=33 LAN; n=31 PBO) received prior OCT LAR (n=56) and/or short-acting OCT (n=24). The frequency of moderate or severe diarrhea and/or flushing decreased in both naive and prior OCT pts treated with LAN (Table). The least square mean percentage of days with moderate or severe diarrhea and/or flushing was significantly lower for pts treated with LAN (23.4%) vs PBO (35.8%) (P=0.004, analysis of covariance adjusted for prior OCT use, region, and baseline values). By week 12, 5HIAA levels dropped by ≥30% to normal in 35% of OCT-naive pts and 29% of prior OCT pts treated with LAN. Among PBO pts, 5HIAA reductions were seen in 15% of OCT-naive pts and 7% of prior OCT pts. Conclusions: Pts showed improvement in CS symptoms of flushing and diarrhea and reduction in 5HIAA levels with LAN treatment, indicating efficacy of LAN in pts regardless of prior OCT use. Clinical trial information: NCT00774930; and EudraCT 2010-019066-92