Suggest how chemotherapy may sometimes be ineffective at killing leukaemia cells.

Chemotherapy may sometimes be ineffective at killing leukemia cells due to several reasons:

1. Resistance to Drugs: Leukemia cells can become resistant to the drugs used in chemotherapy. This can happen if the cells mutate and change in a way that the drug is no longer able to attach to the cell and kill it.

2. Location of Cells: Some leukemia cells may hide in the bone marrow or other parts of the body where the chemotherapy drugs have difficulty reaching. This can make it hard for the treatment to effectively kill all the cancer cells.

3. Rapid Cell Division: Leukemia cells often divide and grow very quickly. If the chemotherapy drugs are not able to kill the cells faster than they can divide, the treatment may not be effective.

4. Side Effects: Chemotherapy drugs are very powerful and can have severe side effects. These side effects can sometimes limit the amount of the drug that can be given to a patient, which can make the treatment less effective.

5. Individual Differences: Each person's body reacts differently to chemotherapy. Some people's bodies may be able to tolerate higher doses of the drugs, while others may not. This can affect how effective the treatment is at killing the leukemia cells.