Acute Myelocytic Leukemia (AML) Associated with Orbital Granulocytic Sarcoma (OGS) in Turkish Children
Prof. Ayhan O. Çavdar



This presentation covers our 40 years of experience and studies (1963-2003) on acute myelocytic leukemia (AML) in Turkish Children in the Pediatric Oncology- Hematology department and Research Center of Ankara University (Turkey). Extramedullary leukemia (EML) in the form of orbital granulocytic sarcoma (OGS), historically called “chloroma", is rare in the Western World. However, the frequency of OGS in Turkish children is very high, ranging from 35% (1971) to 26% (2003). Interestingly, OGS in Turkish Children is usually a presenting feature of AML and is manifested as exophthalmos (proptosis) caused by orbital masses, which may sometimes be clinically apparent. EML in other parts of the body is sometimes found, although much less often.

The factors governing the occurrence of OGS in AML are not well known and there was little information, even of a descriptive nature, in the literature when we first became aware of it. Therefore, in the hope of identifying patient or disease characteristics associated with its occurrence, we have conducted a number of studies in AML patients with and without OGS over the course of many years, using methods and techniques available in our center. Analyses performed and techniques used are listed below:

- Hematological tests: Complete blood counts and bone marrow (BM) examinations including morphologic and cytochemical evaluation, FAB classification, and electron microscopic (EM) evaluation.
- Orbital biopsies were obtained before treatment in several cases and examined by light and EM
- Cellular immunity was evaluated by delayed hypersensitivity tests (PPD and DNCB) and T-cell subsets (T₃, T₄, T₈) quantification by monoclonal antibodies prior to therapy.
- Cytogenetic analysis was carried out with available techniques at the time, but has including G-banding and, more recently, high resolution banding.
- Immunophenotypic analysis of BM cells, including assessment of "stem cell markers" (CD34, HLA-DR) by flow cytometry.
- Multidrug resistance (MDR) as p-glycoprotein (pGp) expression was determined by immunocytochemistry.
- Adhesion molecules (CD56, CD44, CD11a) on blast cells were also evaluated by immunocytochemistry.
- Viral studies for Epstein-Barr virus and C-type RNA viruses were carried out using various tests.

RESULTS

The majority of AML patients with OGS were from "low socio-economic status" (SES). Patient and leukemia characteristics were as follows:

- Age ranged from 8 months to 16 years in patients with OGs and, initially, a predominance of males was noted.
- Hematological findings did not differ significantly in AML cases with and without OGS. AMML (FAB-M4), was the most common subtype of AML and equally frequent in both groups.
- T cell immunodeficiency was demonstrated prior to treatment.
- Cytogenetic analysis revealed more heterogeneity in AML patients with OGS compared to those without OGS, The most common abnormality was t(8:21), (q22; q22) in both groups of AML. However, t(1;11), (p36;q23), double Philadelphia chromosome and hyperdiploidy were observed only in AML group with OGS. - Orbital biopsies revealed leukemic infiltration with cells similar to those found in bone marrow (by light and electron microscopy).
- EBV antibodies to the viral capsid antigen were significantly elevated.
- C-type RNA virus: Electron microscopice examination of leukemic cells revealed “virus like particles" and nucleocapsid-budding.
In addition, C-type RNA virus reverse transcriptase was detected in orbital tumor tissue of AML patients with OGS.
- Multidrug resistance: p-Gp expression was positive in nearly 50% of the AML patients with OGS studied.
- Adhesion molecules: CD56 and CD44 expression were positive in 50% and 90% of the patients with OGS respectively, but not in other AML patients.
- Serum and particularly urinary muramidase levels were higher in the OGS group.


Treatment

Chemotherapy of these patients varied from “monotherapy" (1963) to intensive combination chemotherapy regimens over the course of the study period. Response to treatment and the survival of the 33 patients with AML and OGS were first analyzed in 1988 and despite the use of similar chemotherapy regimens, a retrospective analysis of survival suggested a significantly worse survival in patients with OGS (median 8.7 months) compared to AML patients without OGS (median 28.6 months; p<0,01). Although there were some improvements in CR rate with more intensive chemotherapy regimens (e.g., the Denver Protocol: CCSG-213, and more recently, CCSG-2961), the patients with OGS continue to have a poorer prognosis. However, most such patients were classified as falling into the high-risk subgroup of AML, which could account for their worse outcome.

In conclusion, these findings suggest that there are biological differences between AML with and without OGS in Turkish children. OGS is not associated with a single FAB subtype, but is more frequently of FAB-M4 type. Although associated with poor SES and advanced disease, the latter does not appear to be a sufficient explanation
for OGS.