The purpose of this study is to determine whether the cancer vaccine tecemotide (L-BLP25) in addition to best supportive care is effective in prolonging the lives of subjects with unresectable stage III non-small cell lung cancer, compared to best supportive care alone.

A local ancillary (sub) study in European centers will evaluate the immune response in peripheral blood after tecemotide (L-BLP25) or placebo vaccination.

Ancillary Trial: An exploratory investigation of immune response in peripheral blood after tecemotide (L-BLP25) or placebo vaccination.

The ancillary study is a sub-study within START. This is an exploratory investigation of the immune response in peripheral blood after tecemotide (L-BLP25) or placebo vaccination. The main objective is to evaluate whether administration of single-shot, low-dose cyclophosphamide followed by tecemotide (L-BLP25) vaccinations induces specific immune response in peripheral blood to BLP25 (the mucinous glycoprotein 1 [MUC1] antigen) as well as a modulation of cellular and soluble components of the immune response in subjects with unresectable stage III NSCLC.

Twenty-five of the European START sites will participate in the ancillary study.

Sample size: up to 60 to 80 subjects

All inclusion criteria specified in the START clinical trial protocol except for hemoglobin >= 100 gram/Liter (g/L)

All exclusion criteria are the same as specified in the START clinical trial protocol

Schedule of events: Blood samples will be taken at baseline, visit week 4, 8 13 and 25 (80 milliliter (mL) whole blood each)

Inclusion Criteria:

• Histologically or cytologically documented unresectable stage III non-small cell lung cancer (NSCLC)
• Documented stable disease or objective response, according to Response Evaluation Criteria in Solid Tumors (RECIST), after primary chemoradiotherapy (either sequential or concomitant) for unresectable stage III disease, within 4 weeks (28 days) 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 Gray (Gy). Subjects must have completed the primary thoracic chemo-radiotherapy at least four weeks (28 days) and no later than 12 weeks (84 days) prior to randomization. Subjects who received prophylactic brain irradiation as part of primary chemo-radiotherapy are eligible
• Geographically accessible for ongoing follow-up, and committed to comply with the designated visits
• An Eastern Cooperative Oncology Group (ECOG) performance status of 0-1
• A platelet count > 140 x 10^9/Liter; white blood cells (WBC) > 2.5 x 10^9/Liter and hemoglobin > 90 gram per liter (g/L)

Exclusion Criteria:

Pre-Therapies:

• Undergone lung cancer specific therapy (including surgery) other than primary chemo-radiotherapy
• Receipt of 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) within 4 weeks (28 days) prior to randomization
• Receipt of investigational systemic drugs (including off-label use of approved products) within 4 weeks (28 days) prior to randomization

Disease Status:

• Metastatic disease
• Malignant pleural effusion at initial diagnosis and/or at study entry
• Past or current history of neoplasm other than lung carcinoma, except for curatively 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 5 years
• Autoimmune disease
• A recognized immunodeficiency disease including cellular immunodeficiencies, hypogammaglobulinemia or dysgammaglobulinemia; subjects who have hereditary or congenital immunodeficiencies
• Any preexisting medical condition requiring chronic steroid or immunosuppressive therapy (steroids for the treatment of radiation pneumonitis are allowed)
• Known Hepatitis B and/or C

Physiological Functions:

• 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

Standard Safety:

• Pregnant or breast-feeding women, women of childbearing potential, unless using effective contraception as determined by the investigator
• Known drug abuse/alcohol abuse
• Legal incapacity or limited legal capacity