Fast-Her: Fasting Effects on Breast Cancer Treatment

July 9, 2026 updated by: University of Minnesota
We hypothesize that promoting a fasting state will strengthen the anti-cancer effects of PI3K inhibitors in metastatic breast cancer (MBC) treatment. The primary objective of this study is to assess acceptability of prolonged fasting in this population.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

15

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • United States
    • Minnesota
      • Minneapolis, Minnesota, United States, 55455
        • Recruiting
        • University of Minnesota
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age ≥18 years
  • Histologically confirmed metastatic breast cancer
  • Menopausal or medically ovarian suppressed
  • Currently receiving capivasertib therapy (2 tablets twice daily, 4 days per week)
  • Stable on current capivasertib regimen for at least 2 weeks
  • an ECOG performance status of 0-1
  • BMI ≥25kg/m2
  • Able to provide informed consent
  • Willing to comply with study procedures including CGM wear, food tracking by mCC app and dietary modifications
  • Access to smartphone or tablet for mobile application use

Exclusion Criteria:

  • Type 1 diabetes mellitus
  • Uncontrolled type 2 diabetes (HbA1c >9.0%)
  • History of severe hypoglycemia
  • Eating disorders or contraindications to fasting
  • Pregnancy or breastfeeding
  • Significant gastrointestinal disorders affecting food absorption
  • Unable to fast for medical reasons
  • Concurrent participation in other dietary intervention studies
  • A history of significantly abnormal lab results within 4 weeks of consent date, such as hematologic (Hgb < 10.0, platelets < 100), hepatic (LFTs > 2X nl), renal (Cr > 1.5)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Supportive Care
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Sequence A

Participants randomized to Sequence A will complete a normal eating intervention period, followed by a washout period, followed by a prolonged fasting intervention period.

Normal eating → Washout → Prolonged fasting
Behavioral: Normal Eating
During the normal eating intervention period, participants will follow their usual eating pattern. Participants will continue their prescribed PI3K inhibitor dosing, with medications taken at standardized times to ensure consistent pharmacokinetic measurements.
Behavioral: Prolonged Fasting
During the prolonged fasting intervention period, participants will eat only once daily (dinner), with water, black coffee, and tea permitted during fasting hours. Participants will continue their prescribed PI3K inhibitor dosing, with medications taken at standardized times to ensure consistent pharmacokinetic measurements.
Active Comparator: Sequence B

Participants randomized to Sequence B will complete a prolonged fasting intervention period, followed by a washout period, followed by a normal eating intervention period.

Prolonged fasting → Washout → Normal eating
Behavioral: Normal Eating
During the normal eating intervention period, participants will follow their usual eating pattern. Participants will continue their prescribed PI3K inhibitor dosing, with medications taken at standardized times to ensure consistent pharmacokinetic measurements.
Behavioral: Prolonged Fasting
During the prolonged fasting intervention period, participants will eat only once daily (dinner), with water, black coffee, and tea permitted during fasting hours. Participants will continue their prescribed PI3K inhibitor dosing, with medications taken at standardized times to ensure consistent pharmacokinetic measurements.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Effect of plasma from fasting in patients on PI3K inhibitors on cell viability
Time Frame: Week 2 of prolonged fasting
We will culture 2D/3D breast cancer models using plasma from patients in the fed and fasted states. We will assess tumor cell viability by measuring cell proliferation, apoptosis, and cell cycle distribution.
Week 2 of prolonged fasting
mechanisms by which fasting might enhance PI3K inhibitor efficacy through complementary molecular and cellular studies
Time Frame: Week 7
We will culture 2D/3D breast cancer models using plasma from patients in the fed and fasted states and perform metabolomic and proteomic analyses to evaluate the effects on insulin and PI3K pathways.
Week 7
Identify biomarkers/patient characteristics predicting the enhancement of PI3K inhibitor efficacy with fasting.
Time Frame: Week 7
We will evaluate biomarkers that may predict the influence of fasting on PI3K inhibitor efficacy. Using serial plasma samples, we will analyze PI3K inhibitor pharmacokinetics, metabolic markers (e.g., insulin, glucose), circadian markers (melatonin, cortisol), and tumor-specific markers (circulating tumor DNA).
Week 7

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Minnesota

Investigators

  • Principal Investigator: Lisa Chow, MD, MS, University of Minnesota

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

May 18, 2026

Primary Completion (Estimated)

July 1, 2027

Study Completion (Estimated)

July 1, 2027

Study Registration Dates

First Submitted

May 28, 2026

First Submitted That Met QC Criteria

May 28, 2026

First Posted (Actual)

June 3, 2026

Study Record Updates

Last Update Posted (Actual)

July 13, 2026

Last Update Submitted That Met QC Criteria

July 9, 2026

Last Verified

July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • MED-2025-34235

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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