Study of Tecemotide (L-BLP25) in Participants With Stage III Unresectable Non-small Cell Lung Cancer (NSCLC) Following Primary Chemoradiotherapy

Inclusion Criteria: * Receipt of concomitant or sequential chemoradiotherapy, consisting of a minimum of two cycles of platinum-based chemotherapy and a minimum radiation dose of greater than or equal to (\>=) 50 Gray (Gy). Participant must have completed the primary thoracic chemoradiotherapy at least 4 weeks and no later than 12 weeks prior to randomization * Written informed consent given before any study-related activities are carried out. * Histologically or cytologically documented unresectable stage III NSCLC. Cancer stage must be confirmed and documented by Computed Tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET) scan * Documented stable disease or objective response, according to RECIST, after primary chemoradiotherapy for unresectable stage III disease, within four weeks prior to randomization * Receipt of concomitant or sequential chemoradiotherapy, consisting of a minimum of two cycles of platinum-based chemotherapy and a minimum radiation dose of \>= 50 Gy * Eastern cooperative Oncology Group (ECOG) performance status of 0 or 1 * Adequate bone marrow function * Greater than or equal to 20 years of age Exclusion Criteria: * Lung cancer-specific therapy (including surgery), other than primary chemoradiotherapy. Note: exploratory surgery before study entry is allowed * Immunotherapy (e.g., interferons, tumor necrosis factor \[TNF\], interleukins, or biological response modifiers \[granulocyte macrophage colony stimulating …