How to treat 15cm malignant lung tumor should be further analyzed with the spreading degree of malignant tumor and pathological type of the patient. 15cm malignant lung tumor is considered as a very big lung tumor, usually the cancer cells have already spread, and it is impossible to remove the cancer cells completely by surgery, so it is necessary to carry out radiotherapy, chemotherapy, targeted therapy and other treatments to remove the cancer cells as much as possible, so as to create the conditions for further surgical treatments, and the specific treatments need to be combined with the degree of spread of the cancer and the type of the cancer cells and other analyses. The patient’s situation is relatively serious, but he should still actively receive treatment. Although the treatment may not be able to achieve a complete cure, it can effectively stop the rapid development and spread of cancer cells and prolong the patient’s life cycle.