[1566] Can Bone Marrow (BM) Immunohistochemistry Predict Recurrent or Relapsed Disease in Acute Myeloid Leukemia (AML) Following Induction Chemotherapy?

Ryan E Swapp, Curtis A Hanson, James D Hoyer. Mayo Clinic, Rochester, MN

Background: Assessment of residual acute AML in day 14 post-treatment bone marrow biopsies is a common diagnostic dilemma. Immunohistochemical (IHC) stains for CD33, CD34 and CD117 are sometimes used to assess the leukemic cells. The goal of our study was to determine the utility of these stains in conjunction with morphologic features in predicting a subsequent marrow relapse.
Design: 42 cases of CD34+ AML were identified that had pre- and post-induction BM biopsies available for evaluation; BM were obtained from day 11 to day 18 following induction chemotherapy. IHC stains (CD33, CD34, CD117) were done on both pre- and post-induction BM biopsies. Morphologic features evaluated on post-treatment biopsies included cellularity (%), blasts (% of total cellularity), and clusters of blasts (≥3 cells); this assessment was done in blinded fashion without knowing subsequent outcome. Follow-up data for outcome (remission or residual/relapse at <1 mo., 1-6 mos, and 6-12 mos) were then recorded.
Results: Table. Post-treatment BM biopsy (day 11-18)

Conclusions: Marked BM hypocellularity (≤5%), low blast count by CD34 IHC (≤5%), and lack of blast clusters by CD34 at day 14 post-induction chemotherapy were excellent predictors for maintaining remission for at least 12 mos. in patients with AML. Conversely, BM cellularity >5%, an increased blast percentage, and clustering of blasts had a high predictive value of relapse within the first month of treatment. CD33 IHC was not helpful for detecting residual disease due to nonspecific staining. CD117 also added no additional value as it was similar to CD34 staining and is also present on normal hematopoietic precursors, including pronormoblasts. BM assessment of cellularity and blast % using CD34 are optimal for assessing residual disease of AML on BM biopsies immediately following treatment and may indicate which patients require closer clinical followup.
Category: Hematopathology

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 240, Monday Morning


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