Pilot study assessing 18F-fluorothymidine PET/CT in cervical and vaginal cancers before and after external beam radiation

• Standard uptake values of FLT were compared with FDG-PET in GYN cancer patients.
• FLT tracer uptake markedly decreased after chemoradiation therapy (chemoRT).
• There may not be a significant effect of inflammation on FLT uptake after RT.

ObjectiveThe role of F-18-fluorothymidine (FLT) PET-CT imaging in the evaluation of gynecologic cancers has not been established. We sought to evaluate (FLT) PET-CT imaging in gynecologic cancers by comparing standard uptake values (SUVs) of FLT with F-18-fluorodeoxyglucose (FDG) PET in the primary tumor at diagnosis, and assess FLT uptake immediately following concurrent chemoradiotherapy (chemoRT).MethodsIn this pilot study, patients treated for cervical (5) or vaginal (1) cancer underwent FLT-PET and FDG-PET scanning at diagnosis (FLT1 and FDG1). Five patients (4 cervical and 1 vaginal) also underwent FLT-PET within 1–3 weeks after chemoRT before brachytherapy (FLT2). Wilcoxon rank-sum test was used to compare the FLT1 and FDG1 parameters.ResultsMedian age at diagnosis was 61-years (range, 33–72). Cervical cancers were staged as IB2 (n = 1, 20%), IIB (n = 1, 20%), IIIB (n = 1, 20%) and IVA (n = 2, 40%) and the single vaginal cancer was staged IIIB. The most common histology was squamous cell carcinoma (n = 3, 50%) followed by adenocarcinoma (n = 2, 33%) and clear-cell adenosquamous carcinoma (n = 1, 17%). Median tumor SUVmax at diagnosis was 7.8 on FLT1-PET (3.9–14.2) versus 11.6 (5.9–23.2) on FDG1-PET (p = 0.15). Tumor SUVmax of FLT declined 54%–100% after chemoRT.ConclusionThe tumor SUV of FLT at diagnosis was lower than that of FDG-PET. FLT uptake was markedly decreased after chemoRT. Results indicate that there may not be a significant effect of inflammation on FLT uptake in gynecologic cancers. FLT may be a useful tool when assessing the effects of chemoRT on gynecologic malignancies and planning for postchemoRT brachytherapy treatments.