PREDICTIVE POTENTIAL OF TESTING FOR BONE-MARROW INVOLVEMENT IN EWING TUMOR PATIENTS BY RT-PCR - A PRELIMINARY EVALUATION

EWS/ets-oncogene fusion transcripts can he detected in at Beast 98% of Ewing tumors [(ET) Ewing sarcoma and peripheral primitive neuroectode rmal tumor] by reverse transcriptase-polymerase chain reaction (RT-PCR ), thus confirming the histopathologic diagnosis, To detect: minimal a mounts of tumor cells in the bone marrow (BM), we used an RT-PCR assay with a high sensitivity, revealing one tumor cell in a background of 10(6) normal cells. We examined BM samples from 35 newly diagnosed ET patients (23 with localized and 12 with metastatic disease), At diagno sis, tumor cells in the BM were detected in 7/23 patients with localiz ed disease (30%), Fifty percent of patients with isolated lung metasta sis were RT-PCR positive (3/6), whereas 6/6 patients with bone metasta ses showed positive signals (100%), Ail patients with initial PCR posi tivity in the BM became negative during treatment, After a median foll ow-up of 30 months, relapses were observed in bath groups of patients with localized disease (3/7 RT-PCR positive and 2/16 RT-PCR negative). The only recurrence in the group with isolated lung metastases occurr ed as progressive lung disease in 1 of the 2 RT-PCR-negative patients, whereas among the 6 patients with bone metastases 2 remain in complet e remission. So far, RT-PCR screening for SM involvement did not allow prediction of early relapse in ET, To assess better the significance of this test in the evaluation of long-term prognosis and in monitorin g the effectiveness of systemic therapy, long observation periods are warranted before it becomes a tool for treatment stratification. (C) 1 998 Wiley-Liss, Inc.