A number of regimens are available for blast phase disease, but none are satisfactory.^75–79 A combination we prefer employs HU, 6-mercaptopurine, and prednisone, drugs that can be given orally. A hematologic response rate (complete and partial remission) of approximately 30% has been achieved.⁷⁶ This modest improvement in response is characterized by a median remission duration of 7 months, as compared with a survival time of 2 or 3 months for patients with no response.

Although a vincristine/prednisone combination is especially useful in other lymphatic malignancies, in our experience, the survival in lymphoid blast crisis was not significantly increased over that of myeloid blast crisis, even with such tailored chemotherapy. A recent study confirmed these results.⁷⁷ Detailed cytogenetic and molecular studies have not been reported in any of the trials. This suggests that therapeutic responsiveness in the blast crisis may depend on the inherent sensitivity of the blast cells regardless of type, rather than on the inherent effectiveness of the therapeutic regimen.