How long it takes to treat small-cell lung cancer depends on what kind of chemotherapy regimen is given. Chemotherapy regimens for small-cell lung cancer mainly include EP regimen, combined immunotherapy, and radiotherapy. 1. EP regimen: EP regimen is the most commonly used treatment for small-cell lung cancer, which mainly includes first-line chemotherapy drug etoposide or irinotecan, combined with cisplatin or carboplatin, with a total of 4-6 cycles, each cycle of intravenous drip for 3 days, and a cycle of 21 days, and adjuvant chemotherapy is recommended to patients with surgical resection. 2. Combined immunotherapy: most of the small cell lung cancers are in extensive stage when they are found, on the basis of chemotherapy, PD-1 immunotherapy can be combined with PD-1 immunotherapy, which can be given once every three weeks by intravenous drip, so giving chemotherapy combined with PD-1 immunotherapy does not have any effect on the treatment cycle. 3. Radiotherapy: radiotherapy is usually combined with chemotherapy to treat small-cell lung cancer, the irradiation dose is usually 40-70Gy, and irradiation is divided into 5-7 weeks, and the commonly used radiation lines are electron beam B line, neutron gas pedal and so on. Therefore, how long does it take to treat small cell lung cancer needs to be determined according to the cycle of treatment program after the clinician formulates the treatment program.