Importance: Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) can affect patient health-related quality of life (HRQoL). Appropriate information may improve their adherence to treatment and quality of life. Objective: To evaluate the change in patient's perceptions of the level of information at lanreotide (LAN) treatment initiation for GEP-NETs vs after 6 months. Design: OPERA (NCT03562091) was a prospective, longitudinal, noninterventional study. Setting: Thirty-one centers in France specialized in the management of patients with NETs. Intervention: Planned clinical visits at enrollment and end-of-study visits at month 6, with completion of the European Organisation for Research and Treatment of Cancer 25-item Quality of Life Questionnaire--Information Module (QLQ-INFO25) and 30-item Quality of Life Questionnaire--Core. Main outcome: Absolute change in the patient's perception of the information between baseline and month 6, using the relevant domains of the QLQ-INFO25. Endpoints measured at baseline and month 6 for at least 1 of the 3 targeted QLQ-INFO25 dimensions of the primary endpoint. Results: Ninety-three of the 115 patients enrolled completed ≥1 primary endpoint information dimension. Mean (SD) scores for the primary endpoint information dimensions were high at baseline (disease, 63.41 [20.71]; treatment, 58.85 [19.00]; supportive care, 26.53 [24.69]; maximum 100). There were no significant changes between baseline (98.34% CI) and 6 months (disease, -2.84 [-8.69, 3.01; P = .24]; treatment, -4.37 [-11.26, 2.52; P = .13]; supportive care, 0.46 [-6.78, 7.70; P = .88]), and in HRQoL between baseline and 6 months. Conclusions and relevance: The lack of change in patient's perceptions of the disease, treatment, and supportive care information provided over the first 6 months of LAN treatment may suggest that physicians provided adequate information at the treatment initiation. [ABSTRACT FROM AUTHOR]