Three sudden deaths occurred in a small clinical trial involving patients treated with arsenic trioxide for recurrent acute promyelocytic leukemia, as recently reported in the journalBlood.
Acute promyelocytic leukemia (APL) is a type of acute myeloid leukemia. APL is a cancer of the white blood cells. 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. Standard initial treatment for patients with APL consists of chemotherapy, including trans-retinoic acid and an anthracycline-based compound. Historically, patients who did not respond to initial therapy, or who had a cancer recurrence following initial therapy, were simply re-treated due to the lack of options of effective treatments for this disease. Recently, however, the Food and Drug Administration (FDA) approved arsenic trioxide for patients with APL who have failed standard therapy, giving patients with this disease an effective treatment option.
Results from a recent clinical trial evaluating differing doses of arsenic trioxide, however, indicate that caution should be used when patients are being treated with arsenic trioxide. In this clinical trial, 3 out of 10 patients died suddenly during their first cycle of treatment. Autopsy results from 2 of the patients did not reveal the cause of death. The other patient who died from treatment had heart failure. One of arsenic trioxide’s known side effects is heart complications. However, these complications are typically transient. Treatment variables surrounding the deaths in this trial have been assessed and show no associations except similar patient characteristics of all 3 patients who died: African American descent, young age and obesity.
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The researchers that conducted this trial warn that caution should be taken with arsenic trioxide used as treatment. Further investigation is underway to determine optimal treatment dosages and possible patient characteristics that may put individuals at risk for complications with arsenic trioxide. Patients with APL considering treatment with arsenic trioxide may wish to speak with their physician about the risks and benefits of the treatment with arsenic trioxide being considered. (Blood, Vol 98, No 2, pp 266-271, 2001)
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