A specific predictor during routine follow-up to ascertain risk for postautologous peripheral blood hematopoietic stem cell transplantation (post-APHSCT) relapse in non-Hodgkin lymphoma (NHL) has not been identified. Thus, we studied if new-onset lymphopenia measured by the absolute lymphocyte count (ALC) was a marker of post-APHSCT NHL relapse. ALC was obtained at the time of confirmed relapse, and at last follow-up with no relapse. From 1993 until 2005, 269 patients treated with APHSCT for diffuse large B-cell lymphoma (DLBCL) were included in this study. Patients at last follow-up without relapse (N = 137) had a higher ALC compared with those with low ALC at the time of confirmed relapsed (N = 132) (median ALC ×109/L of 1.66 versus 0.71, P < .0001, respectively). ALC at follow-up was a strong predictor for relapse with an area under the curve (AUC) = 0.86 (P < .0001). An ALC <1.0 × 109/L at the time of confirmed relapse had a positive predictive value of 89% and a positive likelihood ratio of 8.4 to predict relapse post-APHSCT. Patients with an ALC ≥1.0 × 109/L (N = 147) had a cumulative incidence of relapse of 19% versus 92%, with an ALC <1.0 × 109/L (N = 122) (P < .0001). This study suggests that new-onset lymphopenia measured by ALC can be used as marker to assess risk of DLBCL relapse during routine follow-up for after APHSCT.
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