The cells are tested.

If the genetically-changed stem cells are good:

• The cells are frozen to keep them ready for you.
• They stay frozen for a few months until it is time to put them into your body.

If there are problems:

• The cells will not be used for your treatment.
• They are not put into your body.
• They get destroyed in the laboratory.
• Your doctors might need to collect more cells from you.