What kinda fever persist in cancer?

Several: Breakdown products from tumors can cause fevers as well as biologically active substances which can be secreted as well. Involvement of the brains thermostat area can also result in fever.

Infection and other: If cancer patient is receiving chemotherapy, his/her immune system will decrease and risk of infection is high. If infection is not under control. He/she can have persistent fever. A negative culture or other "work up" does not rule out infection. Some cancer itself if not under control, can cause fever as well. Fever can also induced by drugs.