This pilot observational study is being done to identify possible biomarkers of response to endocrine therapy in patients with ER/PR+ metastatic lobular breast cancer (LBC) starting new endocrine therapy. 18F-fluorofuranylnorprogesterone Positron Emission Tomography/Computed Tomography (FFNP-PET/CT) and liquid biopsies will be performed at baseline and after 4 weeks of treatment. Baseline levels and dynamic on-treatment changes in estrogen signaling as measured by FFNP-PET/CT and circulating tumor cell (CTC) liquid biopsy will be correlated with clinical response to endocrine therapy and progression-free survival in the above cohort of patients.
Who can participate
Age range18 Years
SexALL
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Inclusion criteria
✓. Willing to provide informed consent
✓. Individuals at least 18 years of age
✓. Have biopsy-proven ER/PR-positive (defined as ER ≥1 percent and PR ≥1 percent by IHC) and HER2-negative advanced or metastatic LBC starting new standard of care endocrine therapy
✓. Adequate organ function as indicated by standard laboratory tests (CBC, liver function tests or CMP) allowing for systemic breast cancer treatment per treating oncologist
✓. Patients with evaluable bone-only disease that is lytic or mixed lytic-sclerotic are eligible
✓. Willing to comply with all study procedures and be available for the duration of the study
✓. Disease may be measurable by RECIST 1.1 criteria or non-measurable. Lesion size must be at least 1cm. If only bone lesions present, they should be lytic or mixed lytic-sclerotic. If only liver lesions present, patient is not eligible.
Exclusion criteria
✕. Patients with active brain metastases
What they're measuring
1
Number of Participants who have decreased FFNP uptake on PET/CT in response to endocrine therapy
Timeframe: baseline, 4 weeks
2
Number of Participants who have decrease in circulating tumor cell estrogen signaling in response to endocrine therapy
Timeframe: baseline, 4 weeks
3
Number of Participants who have a decrease in concentration of Circulating Tumor DNA in response to endocrine therapy
. Patients with liver-only disease are not eligible due to high background liver activity related to the radiopharmaceutical's hepatobiliary route of elimination
✕. Unable to lie flat during or tolerate PET/CT
✕. Patients with a history of allergic reaction attributable to compounds of similar chemical or biologic composition to FFNP
✕. Presence of liver failure as judged by patient's treating physician
✕. Individuals who are pregnant, lactating, or planning on becoming pregnant during the study
✕. Not suitable for study participation due to other reasons at the discretion of the investigators
✕. Patients with progesterone-receptor negative disease defined as PR \<1 percent by IHC