High-dose chemotherapy is a type of treatment used for cancer. Chemotherapy, or chemo, is a treatment that uses specific drugs that are formulated to kill cells. Cancer cells divide, mutate, and multiply faster than normal cells and are targeted by the chemo drugs. Typically, low dosages of the drugs are used for treatment, but there are times that may require high dosages of chemo. Rare types of cancer, unresponsive cancer, and relapses are common occurrences where a higher chemo dosage is necessary.
Cancer occurs when cells in the body become abnormal, grow too rapidly, and cause additional normal cells to become abnormal as well. Standard chemotherapy uses low amounts of toxic chemicals to kill these abnormal cells and prevent them from growing out of control and causing damage or tumors. While most cancers respond to chemo treatments in low dosages, some rare types do not respond to low-dose chemo treatments. Rare cancers that typically require and respond to high-dose chemotherapy include testicular cancer and a type of bone cancer called osteosarcoma. Some rare forms of brain cancer, such as primary central nervous system lymphoma, may also be treated with high-dose chemo treatments.
Another case when high-dose chemotherapy may be necessary is with an unresponsive cancer. In some cases, a cancer may be treated with low-dose chemo but does not respond or has returned after a successful treatment. These cancers may be more stubborn and aggressive. Higher cancer stages also make treatment more difficult. All of these instances may require a higher chemo dose during treatment.
High-dose chemotherapy can cause substantial damage to bone marrow. Red blood cells and some immune cells are made in bone marrow. With low, standard-dose chemo, the bone marrow can repair and replace damaged parts, but with higher doses assistance for this process is necessary. For this reason, high-dose chemo is often used with stem cell rescue. Stem cells are used to help the patient’s body replace damaged bone marrow. These stem cells can either be harvested from the patient before treatment begins or from a matching donor.
When the patient’s own stem cells are used, they can be harvested from the patient in two ways. Before high-dose chemotherapy is given, circulating stem cells can be gathered from the blood supply. Bone marrow harvesting can also be done to gather stem cells and a small amount of bone marrow.
Donor stem cells are used in cases where cancer cells are present in bone marrow or if a previous transplant using the patient’s stem cells has failed. Donors can be matched through blood tests. Stem cells are harvested from the donor and are introduced into the patient’s blood supply through an intravenous line. All high-dose chemotherapy treatments must be completed before the transplant occurs.