Pediatric Myelodysplastic Syndrome Medication

Children with myelodysplastic syndrome (MDS) have been treated with a wide variety of drugs. For children with an increased number of blasts, treatment like AML is commonly used. The most frequently used chemotherapeutic agents include idarubicin, dexamethasone, cytarabine arabinoside, fludarabine, etoposide, daunorubicin, L-asparaginase, and thioguanine.

Class Summary

Cancer chemotherapy is based on an understanding of tumor cell growth and of how drugs affect this growth. After cells divide, they enter a period of growth (G1 phase), followed by DNA synthesis (S phase). The next phase is a premitotic phase (G2 phase). Finally, a phase of mitotic cell division (M phase) occurs.

The rate of cell division varies for different tumors. Most common cancers grow slowly compared with normal tissues, and the rate may decrease further in large tumors. This difference allows normal cells to recover from chemotherapy more quickly than malignant cells, and it is in part the rationale for current cyclic dosage schedules.

Antineoplastic agents interfere with cell reproduction. Some agents are cell cycle specific, whereas others (eg, alkylating agents, anthracyclines, cisplatin) are not phase specific. Cellular apoptosis (ie, programmed cell death) is another potential mechanism of many antineoplastic agents.

Azacytidine, decitabine, and lenalidomide (for those with 5q- MDS) are approved for use in adults with myelodysplastic syndrome (MDS). There is currently no data on the safety and efficacy of these drugs in children with MDS.

Cytarabine

An antimetabolite antineoplastic agent, cytarabine is converted intracellularly to the active compound cytarabine-5'-triphosphate, which inhibits DNA polymerase. It is metabolized in the liver, with a half-life of 1-3 h. The agent is widely distributed, including in the central nervous system and tears, after IV administration. It is not active via the oral route.

Pegaspargase (Oncaspar)

Pegaspargase is polyethylene glycol-L-asparaginase. It catabolizes asparagine, which is an essential amino acid for lymphoblast growth. This agent has a half-life of 2-3 wk.

Fludarabine (Fludara, Oforta)

Fludarabine is a 2-Fluoro, 5-phosphate derivative of vidarabine. It is converted to 2-fluoro-ara-A that enters cells; it is phosphorylated to form active metabolite 2-fluoro-ara-ATP, which inhibits DNA synthesis. The half-life of the active metabolite is 9 h.

Idarubicin (Idamycin)

Idarubicin is an anthracycline antineoplastic agent. It inhibits cell proliferation by inhibiting DNA and RNA polymerase. It is metabolized in the liver to active idarubicinol. It has half-life of 14-35 h (PO) or 12-27 h (IV). This agent is a vesicant.

Daunorubicin (Cerubidine)

An anthracycline antineoplastic agent, daunorubicin inhibits DNA and RNA synthesis by intercalating between DNA base pairs. It has a half-life of 14-20 h (23-40 h for active metabolite).

Dexamethasone (Baycadron)

A long-acting fluorinated corticosteroid, dexamethasone induces apoptosis of leukemia cells by means of glucocorticoid receptors. Dexamethasone 0.75 mg is equivalent to 4 mg methylprednisolone, 5 mg prednisolone, 30 mg hydrocortisone, or 25 mg cortisone.

Thioguanine (Tabloid)

Thioguanine is a purine analog with antineoplastic and antimetabolite properties.

Etoposide (Toposar)

Etoposide is a semisynthetic podophyllotoxin with poor penetration of the cerebrospinal fluid (CSF). It inhibits topoisomerase II and causes DNA strand breakage, which arrests cell proliferation in the late S or early G2 portion of cell cycle. It has a half-life of 4-11 h.

Azacitidine (Vidaza)

Azacitidine is approved for use in adults with myelodysplastic syndrome (MDS). It is a pyrimidine nucleoside analog of cytidine. It interferes with nucleic acid metabolism. This agent exerts its antineoplastic effects by DNA hypomethylation and direct cytotoxicity on abnormal hematopoietic bone marrow cells. Hypomethylation may restore normal function to genes critical for cell differentiation and proliferation. Nonproliferative cells are largely insensitive to azacitidine.

Azacitidine is approved for adults by the US Food and Drug Administration for treatment of all 5 MDS subtypes.

Decitabine (Dacogen)

Decitabine is approved for use in adults with myelodysplastic syndrome (MDS). It is a hypomethylating agent believed to exert antineoplastic effects by incorporating into DNA and inhibiting methyltransferase, resulting in hypomethylation. Hypomethylation in neoplastic cells may restore normal function to genes critical for cellular control of differentiation and proliferation.

This agent is indicated for treatment of MDSs, including previously treated and untreated, de novo, and secondary MDSs of all French-American-British (FAB) Cooperative Group MDS subtypes and International Prognostic Scoring System (IPSS) groups intermediate-1 risk, intermediate-2 risk, and high risk.

Lenalidomide (Revlimid)

Lenalidomide is approved for use in adults with myelodysplastic syndrome (MDS). It is indicated for transfusion-dependent MDS subtype of 5q- cytogenetic abnormality. It is structurally similar to thalidomide. This agent has immunomodulatory and antiangiogenic properties. It inhibits proinflammatory cytokine secretion and increases anti-inflammatory cytokines from peripheral blood mononuclear cells. The dose used in MDS is much lower than that used for multiple myeloma.