PCI and Brain MRI Follow-up vs Brain MRI Follow-up Alone in Limited-stage SCLC Patients

Inclusion Criteria:

* Histologically/cytologically proven diagnosis of SCLC.
* Age ≥ 18 years.
* Karnofsky performance status ( KPS) ≥80.
* The limited-stage is defined as the tumor confined to one side of the chest, including ipsilateral hilar, bilateral mediastinum, and bilateral supraclavicular lymph nodes. (The definition of metastatic lymph nodes is that the short diameter ≥ 1cm or PET-CT shows increased metabolism with SUV≥2.5, or proved by mediastinoscopy/EBUS/TBNA biopsy. The thickness of pleural effusion on chest CT is less than 1cm (unless cytology proves to be malignant pleural effusion). According to 8th AJCC/UICC TNM staging system, it is the I-IIIC without intrapulmonary metastasis.
* Patients who have received definitive chest radiotherapy and chemotherapy and achieved complete remission of tumor within 4-6 weeks after the end of radio-chemotherapy (in accordance with the Response Evaluation Criteria in Solid Tumors v.1.1 including enhanced CT scan of chest and abdomen, enhanced brain MRI, bone scan and tumor markers).
* Good follow-up compliance;
* Fully understand this study, and voluntarily sign the informed consent form.

Exclusion Criteria:

* Patients with a history of malignant tumors (past or concurrent) within 5 years, excluding papillary thyroid cancer, non-malignant melanoma skin cancer and cervical carcinoma in situ.
* Patients who have received radical surgery (excluding biopsy).
* Patients with psychiatric history, pregnancy and lactation.
* Uncontrolled diabetes, hypertension, severe active infection.
* Patients with chronic diseases of central nervous system.
* Patients with contraindications of brain MRI examination.
* Other situations deemed unsuitable by the doctor in charge.