A prospective study of 18FDG PET in the prediction of relapse in patients with high risk clinical stage I (CS1) non-seminomatous germ cell cancer (NSGCT): MRC study TE22

Huddart, R., O'Doherty, M., Padhani, A., Rustin, G., Mead, G., Seiby, P., Vasey, P., Wow, M., Kirk, S. and Stenning, S. (2005) A prospective study of 18FDG PET in the prediction of relapse in patients with high risk clinical stage I (CS1) non-seminomatous germ cell cancer (NSGCT): MRC study TE22. EJC Supplements, 24 (18S), 4520.

Abstract

Background: High risk stage I NSGCT is characterised by vascular or lymphatic invasion within the primary tumour. This group comprises ~50% of stage I pts with, (untreated) a relapse rate of 35-40%. Options for the management of such pts include adjuvant chemotherapy, retroperitoneal lymph node dissection (± adjuvant chemotherapy) and surveillance, each achieving similarly high cure rates. An FDG PET scan may be able to aid discrimination between pts without occult metastatic disease, for whom surveillance is an attractive option, and those requiring immediate therapy.
Methods: High risk (vascular invasion +ve) CS1 NSGCT pts underwent FDG PET scanning within ~8 weeks of orchidectomy. PET+ve pts went off study, PET -ve pts were followed on surveillance. The primary outcome measure was the -ve predictive value of PET, defined as the 2-year relapse-free rate (RFR) in pts with a negative PET scan. Assuming a RFR of ~90%, to exclude a RFR < 80% with 80% power (5% significance), ~100 PET negative pts were required from ~135 scanned pts. All baseline CT scans were subject to central review blinded to PET result and relapse status and, in relapsed pts, a retrospective comparison of the CT and PET scan results.
Results: Pts were registered between 5/02 and 1/05, when the trial was stopped early by the independent Data Monitoring Committee due to an unacceptably high relapse rate in the PET-ve pts. 116 pts were registered of whom 111 underwent PET scans. 88 pts (79%) were PET-ve; 87 proceeded to surveillance and one requested adjuvant chemotherapy. With median follow-up of 11 months, 33 of the 87 pts on surveillance relapsed for a one-year relapse-free rate of 63% 90% CI (54%, 72%). The PET +ve/relapse rate was 69% in patients with normal markers pre-orchidectomy (n = 36) and 41% in those with raised markers (n = 66). There has been one death (suicide) amongst the PET -ve pts. The radiology and PET scan review will be completed by May 2006.
Conclusions: Though PET identified a proportion of pts with disease not detected by CT scan the relapse rate amongst PET -ve pts remains high. The study results therefore suggest that 18FDG PET scanning is not able to identify pts at sufficiently low risk of relapse to replace other treatment options in this setting.

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