Purpose: It is known that complete remission (CR) prolongs survival in acute myeloid leukemia (AML). In 2003, less stringent response categories were introduced, most notably CR with incomplete platelet recovery (CRp). Although the significance of CRp for survival remains unclear, reports of AML trials frequently combine CR with CRp rather than considering CR as a separate entity.
Patients and methods: This practice led us to retrospectively examine the effect of CR on outcome in newly diagnosed AML, by using data from 6,283 patients treated on Eastern Cooperative Oncology Group (ECOG) and Southwest Oncology Group (SWOG) protocols or at M. D. Anderson Cancer Center. This effect was then contrasted with the effect of CRp in the M. D. Anderson Cancer Center cohort.
Results: At least 94% of patients receiving cytarabine-based therapy and surviving for more than 3 or 5 years achieved a CR with either initial or salvage therapy; limited data suggest the same for patients receiving initial therapies that did not contain cytarabine. Patients with CR were more likely to live beyond 3 or 5 years than patients with CRp. The likelihood of achieving a CR rather than CRp was greater for patients with AML who had better prognosis. After adjustment for covariates, the relapse-free survival of patients achieving CR was longer than that of patients achieving CRp, whereas patients with CRp survived longer than those with resistant disease.
Conclusion: Our data indicate that CR is of unique clinical significance and should be reported as separate response in trials of newly diagnosed AML. Nonetheless, our findings validate CRp as a clinically meaningful response.