The present invention provides methods for treating tumors in subjects by using a recombinant interferon (rSIFN-co), and optionally, methods for treating solid tumors, such as lung cancer, among others, with or without prior surgery, and as a first line or second line monotherapy or in combination with one or more other anti-tumor therapies. The present invention further provides non-surgical methods for eliminating tumors or reducing tumor sizes in subjects, and/or preventing postoperative tumor recurrence and/or metastases in subjects by using the recombinant interferon (rSIFN-co) which comprises a unique spatial configuration, alone or in conjunction with radiotherapy, chemotherapy, and/or one or more anti-tumor drugs such as biological agents, targeted drugs, small molecules, Traditional Chinese Medicine (TCM) and the like.
