This patient has acute lymphoblastic leukemia (ALL), and the most appropriate treatment is dasatinib with dexamethasone. Diagnosis requires the presence of 25% or more lymphoblasts on bone marrow examination. Cytochemical stains and flow cytometry can help distinguish ALL from acute myeloid leukemia (AML) and B-cell from T-cell ALL. The prognosis for an older patient with ALL has traditionally been poor, with Philadelphia chromosome [t(9;22)] positivity indicating worse outcomes. Twenty-five percent of all adults with ALL and up to 50% of those older than 70 years are positive for t(9;22). With the advent of tyrosine kinase inhibitor (TKI) therapy, medications like imatinib and dasatinib have become the backbone of therapy for Philadelphia chromosome–positive ALL and can be used alone or with chemotherapy. The most significant advance in the treatment of older patients with Philadelphia chromosome–positive disease is TKI therapy. The results of dasatinib and dexamethasone therapy are better than those for traditional chemotherapy, with less toxicity. For older patients who have Philadelphia chromosome–negative ALL, no clear standard cytotoxic chemotherapy regimen exists. However, TKI therapy can provide disease control for greater than 1 year with much less toxicity.

Based on encouraging progress in intensive pediatric regimens, asparaginase has been incorporated into care for adolescents and young adults with ALL. However, use in older adult patients does not improve outcomes and multiplies toxicity.

Anthracyclines (such as daunorubicin), vincristine, and dexamethasone are part of traditional chemotherapy for pediatric and adult patients with ALL; however, results in older patients are disappointing. Therefore, none of these medications would be the best treatment option for this older patient. Combination regimens such as hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone (Hyper-CVAD) can cure adults with ALL, but are too toxic for use in elderly populations. The paradox of ALL in older adults is that although less aggressive regimens are less toxic, they compromise the ability to control the leukemia.