Can there be complications with hepatitis b if i have cancer?

Depends on hep B ,CA: Depends on your hep b (active, inactive, viral load, rx, etc), the type of cancer, and the planned treatment. Co-ordinate your hepatologist (liver specialist) and oncologist (cancer specialist).

Yes: Certain chemotherapy drugs can be toxic to the liver. If you have hep b and cirrhosis, than this will require specialized doses of chemotherapy for you. Additionally, chemo drugs that suppress the immune system can give other infections like viral hepatitis, a "green light" to become more active. Talk with your oncologist for details.