Low incidence of molecular evidence for tumour in PBPC harvests from patients with high risk Ewing tumours

Abstract

Reverse transcriptase polymerase chain reaction (RT-PCR) was applied to evaluate the frequency of tumour cells in PBPC products from 15 high risk Ewing tumour (ET) patients who were treated according to EICESS 92 with high-dose chemotherapy (HDC) and stem cell rescue. Initial tumour cell contamination of the bone marrow (BM) detected by light microscopy was found in five and by RT-PCR in eight cases. RT-PCR was performed on each PBPC sample repeatedly at a sensitivity comparable to 20-100 highly EWS-Fli1 expressing tumour cells per 10 ml of fresh blood. Irrespective of the extent of BM involvement at diagnosis, all BM samples obtained before harvest were RT-PCR negative. Among 12 of 35 analysed apheresis products with single positive RT-PCR results only one sample tested reproducibly positive for tumour cell contamination in independent determinations. These preliminary data suggest that tumour cell contamination of PBPC is rarely found in patients with ET.

Incidence and prognostic value of tumour cells detected by RT–PCR in peripheral blood stem cell collections from patients with Ewing tumour

“…Two other studies have also reported a high incidence of contamination by tumour cells, occurring in either marrow or PBSC grafts of all five patients in both studies (Toretsky et al, 1995;Leung et al, 1998). The incidence of tumour cell contamination of PBSC products in the present study (8%) is more consistent with the findings of three other studies which reported a proportion of patients with tumour cell contamination of PBSC samples of one out of 15 (6.7%), one out of nine (11.1%), and three out of 15 (20%), respectively (Fischmeister et al, 1999;Montanaro et al, 1999;Thomson et al, 1999). This important variability in incidence of tumour cell contamination in PBSC collections in previous reports might be due to different sensitivity and specificity of the techniques of detection, to different times of harvesting and to different disease status at the time of PBSC collection.…”

“…In two other studies tumour cells in BM detected by RT -PCR were observed in two out of the three PBSC-positive patients tested and in three out of the three PBSC-positive patients tested but also in the only PBSC-negative patient, respectively (Toretsky et al, 1995;Leung et al, 1998). Interestingly, in the two series with a low incidence of tumour cell contamination of PBSC collection, no cases of BM micometastases at the time of PBSC collection were observed in the first and only one case in the second study (Fischmeister et al, 1999;Thomson et al, 1999). This observation might suggest that micrometastatic disease in BM should be sought for before collecting PBSC.…”

“…Previous studies on small series of patients with ET have shown that tumour cells might contaminate peripheral sites, including autologous stem cell products from the patient (Toretsky et al, 1995;Leung et al, 1998;Fischmeister et al, 1999;Thomson et al, 1999;Montanaro et al, 1999;Yaniv et al, 2004). Data on the incidence and prognostic value of tumour cell contamination of peripheral blood stem cell (PBSC) collections have been controversial.…”

Ewing Sarcoma tumor cells express CD34: implications for autologous stem cell transplantation

“…19 We and others have previously studied tumor contamination in PBSC harvests from EFT patients and revealed a high incidence of contamination. [15][16][17][18][19] Toretsky et al 15 identified the chimeric transcript in the blood progenitor cell collections of all five of their EFT patients studied. Leung et al 16 studied five high-risk EFT patients and all were reverse transcription (RT)-PCR positive, either in marrow or blood grafts.…”

“…At least one positive collection was identified in one out of nine and 10 out of 15 high-risk EFT patients. 17,18 In our previous study, tumor-contaminated harvests were detected by RT-PCR in all 11 patients in at least one of the collections. 19 In this study, we investigated tumor cell contamination in harvests from EFT patients prior and after CD34 þ selection by RT-PCR and flow cytometry (FC) analyses and studied primary tumor cells for mRNA expression of CD34 by RT-PCR.…”