Amrubicin is primarily used in the treatment of small cell lung cancer (SCLC). It functions as a topoisomerase II inhibitor, which helps in preventing cancer cells from replicating and growing. This makes it effective in slowing down the progression of the disease. Additionally, Amrubicin is sometimes considered for patients who have not responded well to other chemotherapy treatments, offering an alternative option. Its application is carefully monitored due to potential side effects, including myelosuppression and cardiac toxicity, which require regular health assessments during treatment.