Maisonneuve-Rosemont Hospital Université de Montréal

Toxicity of the conditioning regimen

Treatment that cures, but that may also be toxic

All the treatments used to prepare patients for a transplant are referred to as the “conditioning regimen.”

It involves intensive chemotherapy and/or radiotherapy designed to eradicate any remaining tumour cells, as well as the patient’s blood and immune systems. During this period, when patients are said to be in a state of aplasia, and until the HSC transplant helps rebuild those systems, they are dependent upon blood transfusions and vulnerable to infections.

Moreover, this intensive treatment does not only weaken the immune system, it can also have a drastic effect on the body’s other functions and organs. Therefore, all candidates for such a procedure must undergo a thorough pre-transplant medical examination in order to check that all the organs that will be affected are in good health and, if not, that measures are taken to rectify any condition contraindicating a transplant.

Kidney-related complications

Some of the drugs involved in chemotherapy, as well as the immunosuppressors and antibiotics used to prevent and treat infections, are eliminated by the kidneys, which makes them particularly vulnerable to complications. In certain circumstances, they may not be able to work properly, and kidney failure may result. Support must then be provided to enable them to do their job, which is why dialysis may sometimes be used to eliminate the toxic substances that would otherwise accumulate within the patient’s body.

Lung-related complications

Complications involving the lungs may occur because of the heavy penetration of chemotherapy or radiotherapy agents into lung tissue, which may lead to acute respiratory distress syndrome. Such complications are mainly characterized by respiratory failure that will necessitate temporary support for the lungs (an oxygen mask or mechanical respirator) in order to heal the damaged tissue. Respiratory tests are conducted during the pre-transplant medical examination in order to check the state of health of the lungs. It is also imperative that any future transplant patient quit smoking in order to reduce the risk of complications.

Heart-related complications

Cardiac tissue is also very sensitive to the substances found in chemotherapy, especially since heart cells cannot be restored once they have been damaged. A thorough cardiac examination is therefore performed prior to the transplant in order to minimize the risk of any heart-related complications.


As the cells in the reproductive system are extremely sensitive to chemotherapy, there is a very high chance of post-transplant sterility. Patients having to undergo high-dose chemotherapy will be asked to discuss with their doctors the possibility of maintaining their fertility through preserving their sperm or eggs.

Other complications

Other complications may occur if patients have other health problems in addition to their blood-related. The pre-transplant medical examination is then again crucial in determining all the risks that intensive chemotherapy/radiotherapy might involve.