Abstract
Background: The prognosis of patients with early Rai and Binet stage CLL is variable. Recently developed prognostic tests (mutation status, ZAP-70, chromosome evaluation by FISH) require significant technologic expertise and are not available worldwide to most patients with CLL. Smudge cells are ruptured CLL cells appearing on a blood smear. Using a proteomic approach, we recently discovered that the cytoskeletal protein vimentin is expressed at higher levels in CLL cells with unmutated IgVH and that vimentin expression is a marker of poor prognosis in early stage CLL (
Hypothesis: Since vimentin plays an important role in the cytoskeleton and lymphocyte rigidity, we hypothesized that smudge cell formation is inversely correlated with vimentin expression and that the percentage of smudge cells may predict prognosis in CLL.
Methods: We blindly reviewed the blood smears archived at the time of diagnosis of patients with untreated, early stage CLL. A total of 200 lymphocytes and smudge cells were counted per slide and results reported as percentage of total lymphocytes (intact and smudged). The percentage of smudge cells was correlated with vimentin expression measured by flow cytometry, IgVH mutation status, time to treatment (TTT), and survival.
Results: Blood smears of 75 patients were reviewed. The median percentage of smudge cells was 27% (range, 4–72%). The percentage of smudge cells did not correlate with lymphocytosis (r=0.04, p=0.73) and did not change overtime for serial evaluations for individual patients (p=0.61). The percentage of smudge cells appeared to correlate inversely with vimentin expression (r = − 0.627; p = 0.0017). The percentage of smudge cells was higher in patients with mutated IgVH than in patients with unmutated IgVH (median 31% vs. median 13%, p=0.02). The percentage of smudge cells as a continuous variable correlated with both a prolonged TTT (p=0.0023) and overall survival (p=0.04). Patients with less than 30% smudge cells had a median TTT of 72.7 months. The median TTT in patients with ≥30% smudge cells was not reached (p=0.0011), Figure 1.
Conclusion: A lower percentage of smudge cells is associated with unmutated IgVH status and with worse clinical outcome in early stage CLL. The percentage of smudge cells does not vary based on the magnitude of the lymphocytosis, but is patient specific and remains constant over time. Evaluation of the percentage of smudge cells on blood smears could be a universally available prognostic test for patients with early stage CLL.
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Disclosure: No relevant conflicts of interest to declare.
