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 \[granulocyte macrophage colony stimulating factor {GM-CSF}, granulocyte colony stimulating factor {G-CSF}, macrophage-colony stimulating factor {M-CSF}\], monoclonal antibodies) received within four weeks prior to randomization
* Malignant pleural/pericardial effusion or pleural dissemination or separate tumor nodules in the same lobe at initial diagnosis and/or at study entry
* Past or current history of neoplasm other than lung carcinoma, except for adequately treated non-melanoma skin cancer, in situ carcinoma of the cervix, or other cancer curatively treated and with no evidence of disease for at least five years
* Autoimmune disease
* A recognized immunodeficiency disease including cellular immunodeficiencies, hypogamma-globulinemia, or dysgammaglobulinemia; participants who have hereditary or congenital/acquired immunodeficiencies
* Any preexisting medical condition requiring chronic steroid or immunosuppressive therapy, including presence of diffuse radiation pneumonitis spreading out of the involved field
* Known Hepatitis B and/or C
* Clinically significant hepatic dysfunction
* Clinically significant renal dysfunction
* Clinically significant cardiac disease
* Splenectomy
* Infectious process that, in the opinion of the investigator, could compromise the subject's ability to mount an immune response
* Pregnant or breast-feeding women. Participants whom the investigator considers may be at risk of pregnancy will have a pregnancy test performed per institutional standard. Male and female subjects who have a reproductive ability, unless using effective contraception as determined by the investigator throughout the study until at least 6 months after the last study treatment
* Known drug abuse or alcohol abuse
* Legal incapacity or limited legal capacity