Effect of docetaxel on metastatic tumor 18F-fluorocholine uptake in patients with hormone-refractory prostate cancer

Objectives Anti-microtubule agents can cause reductions in tumor 18F-fluorocholine (FCH) uptake, supporting FCH PET as a potential marker of therapeutic response and indicator of resistant metastases in patients receiving chemotherapy. Interim data from an ongoing study evaluating FCH PET/CT for measuring treatment responses in advanced prostate cancer was analyzed to preliminarily investigate the relationship between early and later changes in the FCH uptake and morphology of metastatic lesions following the initiation of docetaxel.

Methods FCH PET/CT was performed at baseline, and after the first (time1) and third (time3) chemotherapy cycles in 10 consecutive patients. Whole body images were acquired 10-15 minutes post-injection of 2.22 to 2.96 MBq/kg of FCH. Region of interest analysis was performed to obtain lesion standardized uptake value (SUV) measurements. The relationship between change in lesion SUVmax from baseline after one cycle of chemotherapy and after 3 cycles was examined using a mixed effects model for clustered repeated measures.

Results A total of 166 lesions were identified (median 26 per patient). Decreasing uptake was noted in 73% and 82% of lesions at time1 and time 3, respectively. Statistically significant changes in lesion SUVmax, but not lesion size, were observed from baseline to time1 and time3. In 1 patient with clinical disease progression, 8 new lesions were identified at time3 . Changes in lesion SUVmax at time1 and time3 were significantly correlated (r=0.70, p<0.001).

Conclusions Significant changes in metastatic tumor FCH uptake may be observed as early as after 1 cycle of docetaxel. These changes may precede morphologic changes, and correlate moderately with changes after 3 cycles. Clinical follow-up is required to determine the prognostic significance of these chemotherapy-related changes in FCH uptake by metastatic prostate cancer.

Research Support This work is supported by NIH/NCI R21CA139687 and NIH/NCRR 5G12RR003061