The present invention relates to treatment of SCLC with therapeutic ADCs comprising a drug attached to an anti-Trop-2 antibody or antigen-binding antibody fragment. Preferably, the drug is SN-38. More preferably, the antibody is an hRS7 antibody and the ADC is sacituzumab govitecan. The ADC may be administered at a dosage of between 4 mg/kg and 16 mg/kg, preferably 4, 6, 8, 9, 10, 12, or 16 mg/kg, mostly preferably 8 to 10 mg/kg. When administered at specified dosages and schedules, the ADC can reduce solid tumors in size, reduce or eliminate metastases and is effective to treat cancers resistant to standard therapies, such as radiation therapy, chemotherapy or immunotherapy. Surprisingly, the ADC is effective to treat cancers that are refractory to or relapsed from irinotecan or topotecan. Preferably, the ADC is administered as a combination therapy with one or more other anti-cancer treatments, such as carboplatin or cisplatinum.
