Natural killer (NK) cells can kill a broad array of tumor cells in a non-major histocompatibility complex(MHC)-restricted manner. Adoptive transfer of NK may prolong the survival of patients with cancer. This study evaluates the efficacy and safety of NK cell-based immunotherapy for small-cell lung cancer (SCLC) after first-line chemotherapy. Half of the participants will receive autologous adoptive transfer of NK cells after the response from first-line chemotherapy, while the other half will be followed up in routine clinal practice.

The small-cell lung cancer (SCLC) is very sensitive to the standard-of-care first-line chemotherapy and/or radiotherapy, but it will ultimately progress or relapse and develop early resistance to conventional treatments. No effective maintenance therapy except for wath and wait after first-line therapy at present.

NK cells constitute the major component of the innate immune system and kill tumor cells in a non-MHC-restricted manner. In our previous pilot study and other reports, adoptive transfer of autologous NK cells expanded ex vivo was very well tolerant and effective.

There is no prospective trial on the maintenance therapy of SCLC after first-line chemotherapy based on autologous NK cells. The purpose of this phase II clinical research is to evaluate the efficacy and safety of autologous NK cells as the maintenance therapy after the first-line treatment, comparing with conventional observation group.

Inclusion Criteria:

• Histologically or cytologically confirmed small cell lung cancer.
• Having completed first-line therapy in the presence of stable disease (SD), partial remission (PR) or complete remission (CR) status.
• Age ≥18 years.
• Karnofsky Performance Status (KPS) ≥80.
• Important organs:cardiac ejection fraction >50%; Pulse Oxygen Saturation(SpO2) >90%; creatinine (Cr) ≤ 2.5 times the normal range; alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤3 times the normal range, total bilirubin (TBIL)≤2.0mg/dl (34.2umol/L);Hgb≥60g/L.
• Without contraindication of apheresis and cell isolation.
• Patients and their families having the willingness to participate in clinical trial with signed written informed consent.

Exclusion Criteria:

• Patient having an active rheumatic immunologic disease.
• Uncontrolled bacterial, fungal or viral infection.
• human immunodeficiency virus(HIV), hepatitis B virus infection(HBV), hepatitis C virus(HCV) infection.
• History of organ transplantation and hemopoietic stem cell transplantation.
• Pregnant or lactating women.
• Patients using immunosuppressive agents within the first 3 months of the study or received glucocorticoid systemic therapy within a week prior to entry into the study.
• Patients receiving other immunotherapy after diagnosis.