CD34 Immunohistochemistry on Day-30 Marrow Biopsy: A Useful Tool for Residual Blast Evaluation in Acute Myeloid Leukemia.
Shalini Verma, Sonam Prakash, Attilio Orazi, Ihsane Ouansafi, Susan Mathew, Daniel M Knowles, Eric J Feldman. Weill Cornell Medical College, New York; Weill Cornell Medical College and New York Presbyterian Hospital, New York
Background: Morphologic evaluation of bone marrow aspirate (BMA) smears is considered the gold standard for detection of residual blasts in post-induction chemotherapy (PC) marrows in patients with acute myeloid leukemia (AML). However, an adequate BMA specimen is sometimes not obtainable in this setting which also precludes reliable evaluation of blasts by flow cytometric immunophenotypic studies (FCIPS) as well as by cytogenetic analysis (CGA). In such cases, blast evaluation of the bone marrow biopsy (BMB) by immunohistochemistry (IHC) may provide a useful alternative. However, in the absence of studies correlating blast counts by IHC with counts based on BMA-morphology and FCIPS, this methodology for residual blast evaluation has gained only limited acceptance by clinicians so far.
Design: Among a group of 107 cases of AML who had achieved complete remission on day 30 marrow specimen by International Working Group guidelines (2003), we studied 54 cases of AML that were CD34(+) at the time of diagnosis and had adequate material for IHC. Sixteen cases with >=5% blasts on day 30 marrow were used as controls. For all cases information on BMA blast count, FCIPS, and CGA was obtained from the pathology reports for both the diagnostic as well as day 30 post chemotherapy marrow specimens. Results of blast frequency at day 30 PC by CD34 IHC were compared with those obtained by BMA morphology, FCIPS and CGA.
Results: The AML cases (28 males, 42 females) ranged in age from 19 to 82 years (mean 59.8 years, median 62 years). Forty cases showed an abnormal karyotype at diagnosis (15 myelodysplasia related, 13 AML with recurrent cytogenetic abnormalities, 12 others). Blast frequency by CD34 IHC on day 30 BMB showed a concordance of 92% with BMA morphology (61/66) (coefficient of correlation r=0.85), 91% with FCIPS (58/64) and 66% with CGA (23/35). All cases that showed <5% blasts on BMA were also negative for residual disease with CD34 IHC. Of the 16 control cases, CD34 IHC identified >=5% blasts in 11 cases (69%), 8 of which (73%) showed CD34(+) blasts in clusters of >=3 cells.
Conclusions: IHC for CD34 is a reliable method for evaluating blast counts in post chemotherapy biopsies of CD34(+) AML, with results comparable to those of BMA smears and FCIPS. Results obtained by IHC can be used to guide therapy decisions in post-induction chemotherapy AML without adequate BMA specimen.
Tuesday, March 1, 2011 1:00 PM
Poster Session IV # 173, Tuesday Afternoon