Molecular imaging of therapy response with (18)F-FLT and (18)F-FDG following cyclophosphamide and mTOR inhibition

Marijke De Saint-Hubert, Lieselot Brepoels, Ellen Devos, Peter Vermaelen, Tjibe De Groot, Thomas Tousseyn, Luc Mortelmans, Felix M Mottaghy

Research output: Contribution to journalArticleAcademicpeer-review


PURPOSE: Evaluation and comparison of 3'-[(18)F]-fluoro-3'-deoxy-L-thymidine (FLT) and 2-[(18)F]-fluoro-2-deoxyglucose (FDG)-PET to monitor early response following both cyclophosphamide and temsirolimus treatment in a mouse model of Burkitt lymphoma.

METHODS: Daudi xenograft mice were treated with either cyclophosphamide or temsirolimus and imaged with FLT-PET and FDG-PET on appropriate days post therapy inititiation. Immunohistochemical (IHC) studies (H&E, TUNEL, CD20, PCNA and ki-67) and DNA flow cytometry studies were performed.

RESULTS: FDG tumor uptake decreased immediately after cyclophosphamide treatment while FLT-PET showed only a late and less pronounced decrease. A fast induction of apoptosis was observed together with an early accumulation of cells in the S-phase of the cell cycle, suggesting DNA repair. Temsirolimus treatment reduced both FDG and FLT tumor uptake immediately after therapy and resulted in a fast induction of apoptosis and G(0)-G(1) phase accumulation.

CONCLUSION: FLT response was less distinct than FDG response and may be controlled by DNA repair early after cyclophosphamide. Nevertheless, FLT-PET was able to reflect decreased proliferation following temsirolimus.

Original languageEnglish
Pages (from-to)110-21
Number of pages12
JournalAmerican journal of nuclear medicine and molecular imaging
Issue number1
Publication statusPublished - 2012


  • Journal Article

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