4FMFES-PET Imaging of Endometrial and Ovarian Cancers

Knowledge of estrogen receptor (ER) status is of paramount importance for breast cancer management. Mounting evidence supports an equally important role of ER status for uterine and ovarian cancers. Indeed, this prognostic factor was shown to stratify survival and progression-free rates, and to predict efficacy of ER-targeting adjuvant hormone therapy in those cancers. Between 70 and 80% of gynecological cancers expresses ER, akin to what is found in breast cancer. However, ER status is assessed by biopsy and hence is limited to primary lesions and to known, accessible metastases.

Commonly used diagnostic tools for gynecological cancers includes anatomical imaging modalities, such as echography, computed tomography (CT) and magnetic resonance imaging (MRI), with an increased role for metabolic [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging, all yielding suboptimal tumor detection rate and poor specificity. Studies explored combination of FDG-PET/CT with [18F]-16α-fluoroestradiol (FES) PET/CT imaging to obtain whole-body assessment of ER status of both uterine and ovarian cancers, with FDG/FES uptake ratio correlating with grade and stage of disease. However, FES has many shortcomings, including rapid hepatic metabolism and binding to plasma globulins, resulting in a strong blood pool and in high nonspecific uptake, both detrimental to tumor detection.

The investigator's research center have designed a novel ER-targeting PET tracer, 4-fluoro-11β-methoxy-16α-[18F] fluoroestradiol (4FMFES) that addresses those flaws; 4FMFES is 2.5-fold more resistant to metabolism and does not bind to globulins. A phase II study comparing FES with 4FMFES-PET in breast cancer patients showed significantly reduced background with 4FMFES, resulting in improved tumor contrast and in an increased tumor detection rate. Preliminary results showed that addition of 4FMFES-PET to the standard FDG-PET allowed upstaging of ~20% of the breast cancer patients studied so far. Those breast cancer derived data forebode the potential of combined FDG- and 4FMFES-PET for whole-body diagnosis and ER status assessment for uterine and ovarian cancers.

Aim: Launch a phase I/II clinical trial evaluating the use of FDG and 4FMFES PET in ER+ uterine and ovarian cancer patients to enhance diagnostic confidence and accuracy, and to assess whole-body ER status non-invasively.

Specific aims:

1. Optimize imaging protocol for abdomen 4FMFES imaging: 4FMFES is eliminated by hepatobiliary excretion and as such generates strong signals in the intestinal tract, which could induce strong background and even false positives. Appropriate timing between 4FMFES injection and scan would allow optimal tumor uptake and minimal unwanted signal in the peritoneal area. Separately, pre-treatment with cholecystokinine (to pre-empty the gallbladder) or with opioids (to prevent intestinal peristalsis) will be explored as alternate ways of optimizing the protocol. A cohort of patients will be constituted in order to explore the best strategy to undertake for the rest of the study.
2. Evaluate the use of combined FDG and 4FMFES-PET for diagnosis and staging of ER+ uterine and ovarian cancers: Two cohorts of both uterine and ovarian cancer patients will be monitored by FDG and 4FMFES-PET/CT in sequence. Tumor uptake for each tracer will be compared. Number of detected lesion per patient using this protocol will be compared to whatever findings CT, or FDG alone would have found, and % of upstaged patients will be reported.
3. Correlate FDG and 4FMFES-PET tumor uptake with biopsy-derived grade and status: Every known, accessible lesion will be biopsied, and tumor grade and receptor status will be assessed. Correlation between pathological characteristics, and FDG and 4FMFES PET-derived tumor uptake will be drawn.

The lack of sensitive and accurate imaging tools for uterine and ovarian cancer means that diagnosis is too often achieved at late onset of those diseases. Not only the validation of 4FMFES-PET combined with standard FDG-PET should yield more precise, whole-body diagnostic and staging, but also could predict prognosis and targeted therapy efficacy.