S Phase Fraction and Aneuploidy in Patients with Aplastic Anemia: Diagnostic and Prognostic Implications.

Aplastic anemia (AA) has variable course and may transform in some patients into paraxysmal nocturnal hemoglobinuria (PNH), myelodysplasia (MDS), or acute myeloid leukemia (AML). Attempts are made to find out indicators that might suggest its future course in order to make prognostic and therapeutic decisions.A proportion of patients with AA may develop cytogenetic abnormalities in due course which may herald the conversion into MDS or AML. The objective of this study was to assess the role of S phase fraction (SPF) and aneuploidy in the early detection of clonal abnormalities in hemopoietic cells.

The study group comprised of 30 patients with AA diagnosed on the basis of peripheral blood and bone marrow findings and 15 healthy controls. All patients were put on cyclosporin (3–5 mg/kg/d) as no one was able to afford either anti-thymocyte globulin or bone marrow transplantation. The patients were followed up periodically for the response to treatment, side effects, and the development of cytogenetic abnormalities. The SPF, aneuploidy, and cytogenetic studies were performed at the start of the study and after 6 months. Peripheral blood cells were stained with propidium iodide and analyzed for SPF and aneuploidy through flow cytometry using Modfit-LT software. Cytogenetic study was performed by conventional method using peripheral blood/bone marrow cells.

The mean age of the patients was 26.8±12.4 years (range 13–58 yrs) and male to female ratio was 4 to 1. The most common clinical presentation was anemia. Other manifestations were bleeding and pyrexia. No etiological association could be made in any of these cases.

Seven patients (23 %) had aneuploidy at the time of diagnosis whereas 3 patients (10%) developed aneuploidy at six months of follow up. The mean SPF value in the controls was 0.47±0.35%. No control subject had aneuploidy. The mean SPF in patients who did not show aneuploidy (n=20) was 0.53 ±0.01% and it was not significantly different from that of controls. The mean SPF value in patients (n=7) who had shown aneuploidy at the time of diagnosis was 3.91 ±0.24% and in patients (n=3) who later on developed aneuploidy was 7.17± 0.38%. The SPF values in both these groups were significantly higher (p=<.001) than in patients without aneuploidy. One patients with aneuploidy later on developed cytogenetic abnormalitity in the form of trisomy 8 and another with aneuploidy developed dysplastic changes in the bone marrow. Out of 20 patients (without aneuploidy) 6 (30%) had shown partial response to treatment whereas 2 (20%) patients with aneuploidy responded. Patients who developed marrow dysplasia or trisomy 8 did not respond to treatment.

We suggest that the measurement of SPF and aneuploidy in patients with AA can be helpful in the prognostic assessment in terms of their propensity to develop dysplasia, cytogenetic abnormalities, or malignancy. Therefore patients with high SPF or aneuploidy may not be advised to undergo immunosuppressive therapy as they may more commonl;y develop into malignancy.