Bortezomib interferes with the growth of some cancer cells and keeps them from spreading in your body. Bortezomib is used to treat multiple myeloma and mantle cell lymphoma. Bortezomib is sometimes given after other cancer treatment. Body fluids should not be handled by a woman who is pregnant or who may become pregnant.This medication may cause blurred vision and may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert and able to see clearly.