Trial Outcomes & Findings for Serial FES PET/CT to Measure Hormone Expression in Patients Undergoing Endocrine Targeted Therapy (NCT NCT04692103)

Last Updated: 2026-01-22

Results Overview

FES uptake will be quantified using lean body mass adjusted SUV (SUL). Percentage change in FES average SULmax between baseline and a second FES scan will be calculated for up to 3 lesions per patient.

Recruitment status

ACTIVE_NOT_RECRUITING

Study phase

PHASE2

Target enrollment

2 participants

Primary outcome timeframe

From time of first F-18 FES-PET/CT scan to time of second F-18 FES-PET/CT scan (approximately 1-12 weeks)

Results posted on

2026-01-22

Participant Flow

Participant milestones

Participant milestones
Measure	Diagnostic (F-18 FES PET/CT) Patients undergo F-18 FES PET/CT scan at baseline. Patients also undergo F-18 FES PET/CT and FDG PET/CT between 1-12 weeks after starting therapy. Repeat FDG PET may be omitted in patients on selective estrogen receptor degrader.
Overall Study STARTED	2
Overall Study COMPLETED	2
Overall Study NOT COMPLETED	0

Reasons for withdrawal

Withdrawal data not reported

Baseline Characteristics

Serial FES PET/CT to Measure Hormone Expression in Patients Undergoing Endocrine Targeted Therapy

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Diagnostic (F-18 FES PET/CT) n=2 Participants Patients undergo F-18 FES PET/CT scan at baseline. Patients also undergo F-18 FES PET/CT and FDG PET/CT between 1-12 weeks after starting therapy. Repeat FDG PET may be omitted in patients on selective estrogen receptor degrader.
Age, Categorical <=18 years	0 Participants n=270 Participants
Age, Categorical Between 18 and 65 years	0 Participants n=270 Participants
Age, Categorical >=65 years	2 Participants n=270 Participants
Age, Continuous	71 years n=270 Participants
Sex: Female, Male Female	2 Participants n=270 Participants
Sex: Female, Male Male	0 Participants n=270 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	0 Participants n=270 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	2 Participants n=270 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants n=270 Participants
Race (NIH/OMB) American Indian or Alaska Native	0 Participants n=270 Participants
Race (NIH/OMB) Asian	0 Participants n=270 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	0 Participants n=270 Participants
Race (NIH/OMB) Black or African American	0 Participants n=270 Participants
Race (NIH/OMB) White	2 Participants n=270 Participants
Race (NIH/OMB) More than one race	0 Participants n=270 Participants
Race (NIH/OMB) Unknown or Not Reported	0 Participants n=270 Participants
Region of Enrollment United States	2 participants n=270 Participants

PRIMARY outcome

Timeframe: From time of first F-18 FES-PET/CT scan to time of second F-18 FES-PET/CT scan (approximately 1-12 weeks)

Population: 2 patients had 2 FES scans each

Outcome measures

Outcome measures
Measure	Diagnostic (F-18 FES PET/CT) n=2 Participants Patients undergo F-18 FES PET/CT scan at baseline. Patients also undergo F-18 FES PET/CT and FDG PET/CT between 1-12 weeks after starting therapy. Repeat FDG PET may be omitted in patients on selective estrogen receptor degrader.
Change in F-18 16 Alpha-fluoroestradiol (FES) Standardized Uptake Value (SUV) - Avg SULmax	78 Percentage decrease in avgSUL Interval 77.0 to 79.0

PRIMARY outcome

Timeframe: From time of first F-18 FES-PET/CT scan to time of second F-18 FES-PET/CT scan (approximately 1-12 weeks)

Population: 2 patients had 2 scans each

Quantitative measures of FES uptake for each disease site will be determined by drawing regions-of-interest on lesions to determine maximal FES uptake (SUVmax) per lesion. Up to 10 sites seen on the static torso survey will be quantified.

Outcome measures

Outcome measures
Measure	Diagnostic (F-18 FES PET/CT) n=2 Participants Patients undergo F-18 FES PET/CT scan at baseline. Patients also undergo F-18 FES PET/CT and FDG PET/CT between 1-12 weeks after starting therapy. Repeat FDG PET may be omitted in patients on selective estrogen receptor degrader.
F-18 16 Alpha-fluoroestradiol (FES) Uptake FES scan 1	5.7 average SUVmax Interval 4.6 to 6.8
F-18 16 Alpha-fluoroestradiol (FES) Uptake FES scan 2	1.4 average SUVmax Interval 1.0 to 1.7

PRIMARY outcome

Timeframe: From time of first F-18 FES-PET/CT scan to time of second F-18 FES-PET/CT scan (approximately 1-12 weeks)

Population: 2 patients had 2 FES scans each

The number of patients showing a 20% increase in FES uptake (SULmean or SUVmax) compared to baseline from the first to second scan using a 90% Wilson score binomial confidence interval.

Outcome measures

Outcome measures
Measure	Diagnostic (F-18 FES PET/CT) n=2 Participants Patients undergo F-18 FES PET/CT scan at baseline. Patients also undergo F-18 FES PET/CT and FDG PET/CT between 1-12 weeks after starting therapy. Repeat FDG PET may be omitted in patients on selective estrogen receptor degrader.
Proportion of Patients With a Threshold of Percentage Change, or That Surpass a Targeted Follow-up F-18 16 Alpha-fluoroestradiol (FES) Standardized Uptake Value (SUV)	0 participants with increased FES uptake

SECONDARY outcome

Timeframe: From start of therapy up to 20 years

Time to disease progression will be measured as the time from the start of endocrine therapy to the time the patient is first recorded as having disease progression.

Outcome measures

Outcome data not reported

Adverse Events

Diagnostic (F-18 FES PET/CT)

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Adverse event data not reported

Additional Information

Hannah Linden, MD

UWashington

Phone: 206-606-2053

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee
Publication restrictions are in place