Day 30 Platelet Count As a Prognostic Marker of Survival in Acute Myeloid Leukemia

Introduction:

Acute myeloid leukemia (AML) affects about 3.5 per 100,000 people per year in the western world. High dose chemotherapy with anthracycline and cytarabine combination has resulted in complete remission rates of around 60% even in elderly patients. Complete remission (CR) is commonly defined as bone marrow blast count of less than 5% with recovery of all three cell lines in the peripheral blood. CR with incomplete count recovery is where there is no evidence of persistent disease but there is an incomplete recovery of blood counts, is also seen frequently and it has been shown to have poor prognosis as compared to patients with normal count recovery. Above normal platelet count is seen in small percentage of patients and the significance of this has not been well described.. We hypothesized that patients with a high platelet count at recovery from induction therapy have an increased survival as compared to those with normal or below normal platelet counts.

Methods:

We did a retrospective chart review of 123 consecutive patients with a diagnosis AML at Georgia Regents University Cancer Center that were admitted for induction treatment between 2005 and 2012. Highest platelet count between days 25 to 35 from the date of initiation of induction chemotherapy was taken for this analysis. Patients were divided into three groups: platelet count <50,000 (n=21); 50,000-400,000 (n=80) & >400,000 (n=22). Stratified survival with Kaplan-Meir curves were calculated for each of the groups.

Results:

Mean follow-up period was 94.122 months and median survival was 33.917 months. Mean survival (in months) for the first group was 23.157; 57.801 for the second group & 187.388 for the third group. Difference between survival curves was statistically significant (p=0.003).

Conclusion:

Patients with complete remission appear to have significant survival advantage as compared to those with incomplete platelet recovery. Review of patients across various large clinical trials from US showed that the patients with CR have 3-5 year survival advantage as compared to those with incomplete platelet recovery. Platelet count at the end of one month after initiation of induction chemotherapy can also be used to predict long-term prognosis. This observation would serve as a valuable addition to the already established prognostic markers such as cytogenetics and molecular studies. Our results need to be validated in a larger set of patients.