DETECTION OF EWING CELLS BY RT-PCR IN PRI MARIES AND PERIPHERAL SITES

The t(11;22) and t(21;22) translocations that are specific for Ewing's tumor are responsible for production of chimeric transcripts between the EWS gene on chromosome 22 and the FLI-1 or ERG gene on chromosome 11 or 21, The development of molecular biology methods capable of dete cting these composites have added to the diagnosis of Ewing's sarcoma. The specific marker can be identified in sites other than the primary , providing the opportunity for studying incipient lesions, Ewing's sa rcoma cells were looked for in blood and/or bone marrow specimens from 46 patients in whom a specific composite had been detected in the pri mary. At diagnosis, 16 of 44 patients had tumor cells in their bloodst ream and 14 of 31 had micrometastases in their bone marrow, Presence o f tumor cells in the bone marrow, but not in the blood-stream, was ass ociated with a greater likelihood of severe metastatic disease. In all the patients who were tested before and after chemotherapy, the blood tests reverted to negative after chemotherapy, and this effect was no t influenced by the quality of the response of the primary to the trea tment. In contrast, patients with positive bone marrow tests after che motherapy were more likely to have a poor response of their primary. B one marrow testing for Ewing's cells at diagnosis and during therapy m ay add substantially to the staging and follow-up of patients with Ewi ng's sarcoma.