Different types of transplant are used in different circumstances to treat retinoblastoma outside the eye.
Autologous peripheral blood stem cell or bone marrow transplants use the patient’s harvested stem cells or marrow.
Allogenic and syngenic transplant use donor stem cells or marrow. They are rarely used for retinoblastoma.
Peripheral Blood Stem Cell Transplant (PBSCT)
Peripheral blood stem cells are immature blood cells found in circulating blood. They are similar to the stem cells found in bone marrow.
Your child’s blood stem cells will be collected in a procedure called apheresis or leukopheresis, similar to dialysis. For 2-4 hours, blood will be circulated through a machine to “harvest” the stem cells, then returned to your child.
If your child has a central venous catheter, this will be connected to the pheresis machine to harvest the stem cells. If she does not have a central line, a special catheter will be placed in a large vein during each session.
4-6 pheresis sessions will be needed to harvest enough stem cells for one transplant. These sessions will usually be timed for about two weeks after regular chemotherapy, when the blood is rich in stem cells as the bone marrow recovers from treatment.
Stem cells can be harvested from umbilical cord blood. However, rarely are enough stem cells obtained this way. Peripheral stem cells will usually be harvested even if the child’s cord blood was banked at birth.
The stem cells will be frozen and returned to your child via intravenous infusion after several days of high-dose chemotherapy.
Peripheral blood stem cell transplant is the most commonly used transplant for children with trilateral or extraocular retinoblastoma.
Autologous Bone Marrow Transplant
Autologous bone marrow transplant is similar to stem cell transplant, but the stem cells are taken from marrow in the hip rather than from peripheral blood.
Your child will be given a short acting general anesthetic. The doctor will then insert a large needle into the bone and remove the bone marrow.
This process is similar to a bone marrow aspiration, used to check whether cancer has spread to the marrow. However, it will be repeated up to fifty times in a single session of about 60 minutes, to remove a total of 1-2 pints of marrow.
Your child’s bone marrow will replenish itself within a couple of days after the harvest. She will be a little sore for several days, and may be tired for several days while the marrow recovers.
The harvested marrow will be frozen until the transplant, and returned to your child via intravenous infusion after several days of high-dose chemotherapy.
Autologous bone marrow transplant is occasionally used instead of peripheral blood stem cell transplant to treat retinoblastoma.
Allogenic and Syngenic Transplant
Allogeneic transplants use stem cells or marrow harvested from a blood relative or unrelated donor. They have much higher risk of complications associated with rejection of the transplant.
Syngeneic transplants use stem cells or marrow donated from an identical twin.
These transplants are most often used to treat leukaemia (blood cancer) and conditions of bone marrow failure, where it is not possible to use the patient’s own marrow or stem cells. They are very rarely used to treat retinoblastoma, and are not discussed here.