The purpose of this study is to evaluate the application value of circulating tumor DNA(ctDNA) with efficacy evaluation and prognostic assessment in patients with unresectable SCLC, who were receiving radiotherapy and chemotherapy treatment.

1. According to each point in time of ctDNA, to analyze the dynamic changes of tumor burden and clonal subtypes which to evaluate the application value of ctDNA in curative efficacy evaluation.
2. Compare the two time points before and after radiotherapy and chemotherapy treatment of the cell free DNA (cfDNA) concentration and tumor burden, analysis the correlation between the changes and prognosis.

Inclusion Criteria:

• Provision of informed consent；
• Newly diagnosed and histological or cytological confirmed extensive stage small cell lung cancer;
• All indicators has confirmed and allow to receive radiotherapy and chemotherapy;
• Follow-up can be carried out and the peripheral blood samples can be collected;
• Cooperate with the provision of clinical pathological data required by the research.

Exclusion Criteria:

• Patients have other primary cancers;
• Patients unable to cooperate with the study for follow-up according to the determined clinical follow-up cycle;
• Unable to accept the judgment of curative effect evaluation by the designated methods such as CT.

treatment extensive stage small cell lung cancer patients

all IPD data for publication

IPD will be shared when the clinical trail is completed.