This is a Phase 3, prospective, multi-center, randomized, double-blind, study evaluating the efficacy and safety of LAN plus BSC versus placebo plus BSC for the treatment of well-differentiated, metastatic and/or unresectable, typical or atypical bronchopulmonary NETs. This study contains two phases: the Double-Blind (DB) Phase, and the Open Label (OL) Phase. The DB Phase includes: Screening, Baseline and Treatment period. The OL Phase will consist of two periods: Treatment Period and Follow-Up Period. The primary objective will be to describe the antitumour efficacy of Lanreotide Autogel/Depot 120 mg (LAN) plus Best Supportive Care (BSC) every 28 days, in terms of progression-free survival (PFS), measured by central review using Response Evaluation Criteria in Solid Tumours (RECIST) v1.1 criteria, every 12 weeks, in subjects randomized to LAN with unresectable and/or metastatic well differentiated, typical or atypical bronchopulmonary neuroendocrine tumours. Recent updates of National Cancer Institute Cancer Network (NCCN) & European Neuroendocrine Tumor Society (ENETS) guidelines recommend SSA in first line for the treatment of locoregional unresectable or metastatic bronchopulmonary NETs as an option beyond ‘observation’ leading to slow and difficult recruitment in SPINET study. Consequently, it was decided to prematurely stop the recruitment in the SPINET study and to transition all subjects still treated in the double-blind phase to the open label (OL) treatment and follow-up phases following respective country approvals of Amendment #5. The new aim of this Phase 3, multicenter, prospective, randomized placebo-controlled clinical study is to describe the antitumor efficacy and safety of Lanreotide Autogel/Depot 120 mg (LAN) plus Best Supportive Care (BSC) in subjects with well-differentiated, metastatic and/or unresectable, typical or atypical, bronchopulmonary NETs.