To investigate the response of temozolomide versus prophylactic cranial radiotherapy in preventing brain metastases in completed or partial remission limited small cell lung cancer patients.

We'd like to investigate the 2-year incidence rate of brain metastases in completed or partial remission limited small cell lung cancer patients who received temozolomide only for 12 months or 25-30Gy prophylactic cranial radiotherapy in preventing brain metastases.

Inclusion Criteria:

1. Histological or cytological diagnosis of small-cll lung cancer histology
2. 18 years or older
3. Eastern Cooperative Oncology Group (ECOG) Performance Status no more than 2
4. Local stage SCLC without distant metastases
5. After 1st-line chemotherapy (EP or IP) at least 4 cycles
6. After radical radiotherapy for primary tumor and lymph node drainage area:including concurrent or sequence chemoradiotherapy
7. CR or PR assessment by RECIST(1.0) before randomized
8. Haemoglobin 10.0 g/dl, Absolute neutrophil count (ANC) 1.5^9/L, platelets 100 x 10^9/L
9. Total bilirubin 1.5 x upper limit of normal (ULN) alanine aminotransferase (ALT) and aspartate aminotransferase (AST) < 2.5 x ULN in the absence of liver metastases, or < 5 x ULN in case of liver metastases
10. Creatinine clearance 60ml/min (calculated according to Cockcroft-gault formula)

Exclusion Criteria:

1. Mixed non-small cell lung cancer histology
2. Neck and supraclavicular lymph node metastasis
3. Be allergic to temozolomide or intolerable to radiotherapy
4. Any unstable systemic disease
5. Pregnant or lactating women