Abstract

Abstract 3847

Acute myeloid leukemia (AML) with inv(3)(q21q26.2)/t(3;3)(q21;q26.2); RPN1-EVI1 [inv3/t3] is a distinct type of AML with recurrent genetic abnormalities (RGA) in the 2008 WHO classification, with poor response to therapy and poor prognosis. The resulting dysregulation of EVI1 plays an important role in stem cell self-renewal and leukemogenesis. Although myelodysplastic syndrome (MDS) with inv3/t3 has a high risk of progression to AML, inv3/t3 is not among the genetic abnormalities sufficient for diagnosis of AML, irrespective of blast percentage (%) in the WHO classification. The revised International Prognostic Scoring System (IPSS-R) includes comprehensive cytogenetic subgrouping to better define prognosis in MDS patients. In this system, inv3/t3 is included in a poor risk karyotype group. The objective of this multicenter study was to evaluate a series of patients with MDS/AML and inv3/t3 in order to characterize their clinicopathologic features and outcome, and to apply the IPSS-R to inv3/t3 MDS patients.

111 patients (40 MDS and 71 AML with inv3/t3) were gathered from 8 medical centers. The median age at diagnosis was 56.5 years and was significantly older in MDS than AML with inv3/t3 patients (65 vs 54.5, p=0.03). Patients typically presented with normocytic anemia, thrombocytopenia and mild leukopenia (median Hb 9.1 g/dL, platelet 91 x109/L, WBC 3.6 x109/L). MDS with inv3/t3 patients had lower WBC than AML with inv3/t3 (median 3.1 vs 5.5, p<0.001). 19% of patients had hepatosplenomegaly. The median bone marrow (BM) blast% was 4% in MDS and 50% in AML with inv3/t3 and BM cellularity was higher in AML (70%) than MDS (40%) with inv3/t3 (both p<0.001). 88% of patients showed dysmegakaryopoiesis with characteristic small uni/bilobated forms. Dysgranulopoiesis (46%) and dyserythropoiesis (56%) were common and 59% of patients displayed multilineage dysplasia. The cytogenetics showed isolated inv3/t3 in 41% of patients, one additional abnormality in 33% and complex karyotype in 26%. −7/del7q (37%) was a frequent additional abnormality. Philadelphia chromosome (Ph) was noted in 10% of AML with inv3/t3. Overall 83% of patients (75% of MDS and 87% of AML with inv3/t3) expired (median follow up of 7.9 months (mo)). Most patients received therapy including 54% with chemotherapy (CTX; topoisomerase II inhibitors and/or antimetabolites) alone, 27% with CTX and allogeneic stem cell transplant (SCT) and 19% with supportive care. 16% of patients (10 MDS and 8 AML with inv3/t3) were associated with prior therapy for solid tumors and lymphomas. 57% of MDS with inv3/t3 patients subsequently evolved to AML.

There was no significant difference in overall survival (OS) between MDS and AML with inv3/t3 (12.9 vs 8.0 mo, Cox PH p=0.11, Figure 1). There was no OS difference between MDS and AML after excluding Ph+ cases (Cox PH p=0.17) nor between de novo and therapy related MDS/AML with inv3/t3 (Cox PH p=0.89). Patients with isolated inv3/t3, one additional cytogenetic abnormality, and a complex karyotype showed progressively shorter OS (12.9, 10.0 and 4.3 mo, Cox PH p<0.001, Figure 2). The patients who received CTX and SCT showed superior OS to patients receiving CTX alone or supportive care only (15, 7 and 5 mo, respectively, Cox PH p=0.02). In multivariate analysis, choice of therapy and complex karyotype retained independent prognostic significance (Cox PH p= 0.02 and p<0.001, respectively).

MDS with inv3/t3 patients were classified into IPSS Intermediate (Int)-1 (21), Int-2 (13), and high (6) risk groups. IPSS-R categorized MDS patients into low (3), Int (6), high (14) and very high (17) risk groups. 57% of IPSS Int-1 risk group patients (expected OS 3.5 year) were reclassified to high or very high risk group in IPSS-R (expected OS <1.6 year). Thus, the IPSS-R scores were higher relative to IPSS score (signed rank test, P<0.001). However, 72.5% and 77.5% of MDS with inv3/t3 patients had shorter OS than expected OS by IPSS-R and IPSS scores.

The IPSS-R better reflects the OS of inv3/t3 than IPSS but may not fully reflect the generally dismal prognosis. Patients with MDS and AML with inv3/t3 follow a similarly aggressive clinical course, supporting classification of MDS with inv3/t3 as an AML with RGA irrespective of blast%. Additional cytogenetic abnormalities are associated with shorter OS in AML/MDS with inv3/t3 and our data suggest that aggressive therapy with SCT should be considered in these patients.

Disclosures:

Vardiman:Celgene Corporation: review of slides for clinical trials not relevant to this abstract Other. Foucar:e. Honoraria–Scientific Symposium Pathology Education: ASCP Press; ARP, Amirsys, ASCP Press; ARP, Amirsys Patents & Royalties, Honoraria, Not relevant to this abstract Other.

Author notes

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