Conditioning /Preparative Regimen

Before your bone marrow or stem cell transplant, you will receive chemotherapy and/or total body irradiation to prepare your body to receive healthy blood stem cells.

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Several days prior to your transplant, you will receive chemotherapy and/or total body irradiation (TBI). This is called the conditioning or preparative regimen.

The purpose of the conditioning regimen is to:

  • destroy your diseased cells
  • suppress your immune system so that the healthy blood stem cells can begin producing new blood cells


Most conditioning regimens include chemotherapy. The exact drugs used with depend on your disease, your overall health and the preferred treatment plan at your transplant center.

Drugs used in the conditioning regimen are sometimes the same as those used in standard chemotherapy to treat the disease. The dosage, however, may be much higher.

Most chemotherapy drugs are given through a thin flexible tube called a catheter or central venous line. The catheter is surgically implanted into a large vein in the neck or chest, placed so it rests just above the heart. It allows the medical staff to give drugs and blood products to you painlessly, and to withdraw the many blood samples required during treatment without inserting needles into your arms.

  • The catheter may be left in place for several months after transplant.
  • Sometimes the catheter is attached to a device called a port that is inserted under your skin.

Total Body Irradiation (TBI)

Some conditioning regimens include total body irradiation (TBI). TBI is typically administered to patients in one or more sessions over a one-to-seven-day period.

You will not actually see or feel the radiation, but you may still find TBI an unnerving experience

  • You will sit or lie still, sometimes in an awkward position, for 10 to 45 minutes while the radiation is administered. This can be difficult, particularly if you are nauseated.
  • Some transplant centers use special stands or boxes to help you remain still during TBI. These can be confining and may make you feel anxious.

Pre-medication with sedatives can help reduce anxiety. Children are usually sedated before TBI to minimize their movement. Very young children may be anesthetized.

It helps to visit the radiation center before TBI therapy begins to familiarize yourself with the equipment and to get your questions answered.

Most centers provide patients with a simulation of TBI so they know, in advance, what to expect, and the health care team can make sure that dosages and equipment measurements are correct.

See the Early Recovery page for details about possible side effects of chemotherapy and TBI.

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Updated June 2024