Chemotherapy
Overview of Chemotherapy for Cancer Treatment
-
Overview of
Chemotherapy for
Cancer Treatment -
Remission-induction
therapy -
Post-remission therapy,
Consolidation Therapy
Overview of Chemotherapy for Cancer Treatment
There are various methods for treating cancer, including surgical therapy, radiation therapy, and chemotherapy. The treatment method varies depending on the type of cancer, and chemotherapy refers to internal drug treatment using anticancer drugs. Acute leukemia is a systemic disease without initial, middle, or final stages, and it can be considered to be in stage 4, which differentiates stages in solid cancers such as stages 1, 2, 3, and 4, due to its nature as a blood disease. Therefore, the basic treatment policy can be based on combined chemotherapy using various types of anticancer drugs, each with a different mechanism of action. Chemotherapy for the treatment of leukemia is carried out with the aim of achieving complete remission and can be divided into remission-induction therapy and post-remission therapy.
Remission-induction therapy
Remission-induction therapy refers to the first round of chemotherapy administered immediately after diagnosis to induce a state of complete remission. It involves the use of combined chemotherapy, where two or more drugs are administered simultaneously or sequentially. The evaluation of chemotherapy is based on the achievement of complete remission.
Complete remission is defined as a state where the blasts (immature cells) in the bone marrow have dropped to less than 5%, leukemia cells are not observed in the peripheral blood, and white blood cells, red blood cells, platelets, etc., are restored to normal while symptoms such as liver, spleen, and lymph node enlargement have disappeared. The chemotherapy administration period is about 7 to 12 days, after which a state of bone marrow function decline occurs, and it begins to recover after an average of about 3 weeks.
Acute Myeloid Leukemia
- For acute myeloid leukemia, representative anticancer drugs used include anthracyclines such as daunorubicin, idarubicin, and mitoxantrone, which have a strong effect on the bone marrow, and cytarabine. The administration period varies depending on the treatment center, but the most common regimen is the "3+7" regimen, where anthracyclines are administered for 3 days and cytarabine is given simultaneously for 7 days. On the 7th day of chemotherapy, a bone marrow examination is performed, and depending on the results, additional chemotherapy can be infused for 2 to 3 more days.
- For a type of acute myeloid leukemia known as acute promyelocytic leukemia (M3 subtype), a different approach is taken. Instead of the drugs mentioned above, an oral drug called all-trans retinoic acid (ATRA, also known as Vesanoid) and an anthracycline anticancer drug like idarubicin are used. ATRA inhibits the excessive proliferation of promyelocytes, which are characteristically seen in the M3 subtype, and induces their differentiation into normal cells.
Acute Lymphoblastic Leukemia
- In the remission induction of acute lymphoblastic leukemia, three types of drugs are basically used: vincristine, anthracyclines, and steroids. To increase the remission rate, cyclophosphamide or asparaginase is added.
- Due to the high risk of relapse in the central nervous system, small amounts of methotrexate, cytarabine, and steroids are administered into the spinal cord. Also, in cases with chromosomal abnormalities (Philadelphia chromosome positive), Gleevec can be taken until the period before consolidation therapy after discharge to maintain remission.
Multiple Myeloma
- Before autologous hematopoietic stem cell transplantation, induction chemotherapy is performed to reduce the many cancer cells spread throughout the bone marrow or body. The systemic chemotherapy is mainly performed with a combination of three drugs: Velcade, Thalidomide, and Dexamethasone. If necessary, local radiation therapy, spinal surgery, plasmapheresis, and dialysis related to kidney failure may also be performed concurrently.
Post-remission therapy, Consolidation Therapy
Achieving a state of complete remission through induction therapy does not mean a cure. This is because if continuous treatment is not carried out, a significant number of leukemia cells remaining in the body that cannot be identified under a microscope will relapse. Therefore, to prevent relapse in a state of complete remission, additional anticancer chemotherapy is performed, which is called post-remission therapy (or consolidation therapy). In the case of acute myeloid leukemia, the drugs used for remission induction are repeated 2-3 times by reducing the dose and administration period, and methods including high-dose cytarabine therapy are also used. Acute lymphoblastic leukemia uses a combination of cytarabine and anthracyclines or methotrexate, and repeats more than three times at intervals of 3-4 weeks.
In addition, after the end of post-remission therapy, maintenance therapy is performed. This method involves administering a low-dose anticancer drug while monitoring the patient in an outpatient setting for about 2-3 years, mainly using drugs such as methotrexate, mercaptopurine, steroids, and vincristine. Unlike acute myeloid leukemia, acute lymphoblastic leukemia has a high risk of relapse to the central nervous system, so small amounts of methotrexate, cytarabine, and steroids are administered into the spinal cord. The duration of chemotherapy is shorter than that of remission therapy, about 5-7 days, and the recovery period is also faster.
In order to increase the cure rate for acute leukemia, differentiated treatment strategies based on individual patient characteristics are needed, and one of the methods for this is hematopoietic stem cell transplantation, which strengthens the patient's immunity.