Safety and Tolerability of LDRT+Sugemalimab+Chemotherapy+Olaparib for First-Line Treatment of SLFN-11 Positive ES-SCLC

The LDRT deals with primary tumour in a 15 Gy of 5fractions over five days, starting from Day 1 in the first cycle.

Etoposide will be administered intravenously at a dose of 100 mg/m\^2 on Days 1, 2 and 3 of each 21-day cycle during the induction phase (Cycles 1-4).

Cisplatin will be administered as intravenous infusion at a dose of 25 mg/m\^2 on Days 1, 2 and 3 of each 21-day cycle during the induction phase (Cycles 1-4).

Sugemalimab will be administered by intravenous infusion at a dose of 1200mg on Day 1 of each 21-day cycle for a maximum of 2 years or progressive disease or intolerable toxicity.

Olaparib will be administered orally at a dose of 150mg qod Day 1,3,5,7 or 150 mg qd/150 mg bid/300mg in the morning and 150mg in the evening/300 mg bid on Day 1-7 of each 21-day cycle for a maximum of 2 years or progressive disease or intolerable toxicity.