Acute leukemia?

I have 5-year-old niece was diagnosed with acute leukemia. He said cured, incurable say. So please explain this disease caused by? By how to cure?

Leukemia is a malignant disease of hematopoietic progenitor cells. Malignant cells lose the ability to grow and differentiate. These cells proliferate in an uncontrolled and then complete replacement of normal bone marrow elements. The majority of cases occur unexplained. However, radioactive and toxic substances (benzene), some chemotherapy, especially procarbarin, melphalan can cause the following diseases or exposure to toxins or chemotherapy induced marrow dysplasia and cause the chromosomal abnormalities.

The majority of patients with acute leukemia have weakness, pale skin, bleeding under the skin, mucous membranes, bleeding gums, nosebleeds, or women with menorrhagia (also cases seek medical attention because swelling interests severe pain and swelling, signs of infection). Blood tests show reduced peripheral 3 cell lines.

Regarding treatment: Acute leukemia ago for this incurable but treatable and potentially cleared by combination chemotherapy and a bone marrow transplant. However, the treatment is also very expensive and long-term.