A method for treating a tumor includes a first treatment procedure using a conventional cancer treatment technique, and a second treatment procedure which includes administering an effective amount of squalamine. The first treatment procedure may be a treatment with one or more conventional cytotoxic chemical compounds. As examples, the cytotoxic chemical compound may be a nitrosourea (such as BCNU), cyclophosphamide, adriamycin, 5-fluorouracil, paclitaxel and its derivatives, cisplatin or other platinum containing cancer treating agents. The cytotoxic chemical compound and the squalamine may be administered by any suitable route. The first treatment procedure may take place prior to the second treatment procedure, after the second treatment procedure, or the two treatment procedures may take place simultaneously. In one example, the first treatment procedure (e.g., a one time intravenous dosage of BCNU) is completed before the second treatment procedure with squalamine begins. As an alternative, the first treatment procedure may be a conventional radiation treatment regimen.