Arsenic: An Effective Treatment for Acute Promyelocytic Leukemia
Trisenox® Is a Standard First Line Treatment for Acute Promyelocytic Leukemia
Trisenox® (arsenic trioxide, ATO) injection in combination with tretinoin (ATRA) is commonly used for the treatment of adults with newly-diagnosed low-risk acute promyelocytic leukemia (APL) whose APL is characterized by the presence of the (15;17) translocation or PML/RAR-alpha gene expression.
Historically APL was treated differently than other forms of acute myeloid leukemia. Initial treatment included the non-chemotherapy drug all-trans-retinoic acid (ATRA), which was most often combined with an anthracycline chemotherapy drug (daunorubicin or idarubicin), sometimes also with cytarabine (ara-c). Recent studies have demonstrated the Trisenox can be used instead of chemotherapy.
Acute promyelocytic leukemia is a type of acute myeloid leukemia. The bone marrow contains early blood-forming cells called stem cells, which grow and mature into 3 blood cell types: red blood cells, which provide oxygen to tissues; platelets, which aid in blood clotting; and white blood cells, which fight infection. APL is characterized by the rapid, uncontrolled growth of specific immature white blood cells, resulting in excess accumulation of these cells in the blood and bone marrow. These leukemia cells crowd the bone marrow, suppressing formation and function of other blood cells, and ultimately invade other parts of the body including the blood, lymph system, and vital organs. In addition, the cancer cells do not function properly, leaving a patient susceptible to infection.
APL is a rapidly growing cancer and treatment must be aggressive for an optimal chance of cure. Approximately 1,500 patients will be diagnosed with APL each year, with an estimated 400 of these patients not responding to initial chemotherapy or experiencing a cancer recurrence following standard treatment.
Trisenox® is indicated for use in APL:
- In combination with tretinoin (ATRA) for treatment of adults with newly-diagnosed low-risk APL whose APL is characterized by the presence of the t(15;17) translocation or PML/RAR-alpha gene expression.
- For induction of remission and consolidation in patients with APL who are refractory to, or have relapsed from, retinoid and anthracycline chemotherapy, and whose APL is characterized by the presence of the t(15;17) translocation or PML/RAR-alpha gene expression.
- For patients with APL who experience a return of cancer following initial chemotherapy, or who no longer respond to standard chemotherapy.
- Trisonex is effective as a single agent in newly diagnosed APL or can be used in combination.
Remissions Induced by Liposomal-Encapsulated All-Trans Retinoic Acid in Newly Diagnosed Patients with APL
All-trans retinoic acid administered orally (oral ATRA) is a component of standard treatment for acute promyelocytic leukemia. Oral ATRA may not regularly lead to either molecular complete remissions or prolonged hematologic complete remissions unless it is combined with Trisonex or chemotherapy.
Liposomes are a drug delivery vehicle. Incorporating anti-cancer agents into liposomes may allow delivery of higher doses or provide more substantial exposure to anti-cancer agents. In fact, clinical studies have already demonstrated that serum levels of ATRA may be higher and maintained longer after treatment with a liposomal-encapsulated ATRA than after orally administered ATRA.
Physicians at MD Anderson Cancer Center in Houston evaluated liposomal-encapsulated ATRA as a single agent for the treatment of patients with acute promyelocytic leukemia. Chemotherapy was only used if evidence of leukemia persisted on 2 occasions following treatment with liposomal-encapsulated ATRA.
Twelve of 18 patients achieved a complete remission (67%) following treatment with liposomal-encapsulated ATRA alone. These results are similar to those achieved using oral ATRA combined with idarubicin chemotherapy.
These physicians concluded that liposomal-encapsulated ATRA alone is an effective means of producing complete remissions in patients with newly diagnosed acute promyelocytic leukemia. The advantage of this approach is that it avoids the toxicity of chemotherapy in the majority of patients. Further studies will have to be performed to identify the best method of using liposomal-encapsulated ATRA.
Sanz, MA, Vellenga E, Rayon C, et al. All-trans retinoic acid and anthracycline monochemotherapy for the treatment of elderly patients with acute promyelocytic leukemia. Blood. First Edition Paper, pre-published online August 3, 2004; DOI 10.1182/blood-2004-04-1642.
Mathews V, George B, Lakshmi KM, et al. Single-agent arsenic trioxide in the treatment of newly diagnosed acute promyelocytic leukemia: durable remissions with minimal toxicity. *Blood.*2006;107:2627-2632.
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