The Medical University of South Carolina has begun a clinical trial examining whether cannabidiol (CBD) can produce measurable biological changes in breast cancer tumors before they are surgically removed.
The randomized, placebo-controlled Phase 1a study is recruiting up to 84 patients with invasive breast cancer at the university’s Hollings Cancer Center in Charleston. The federal clinical trial record lists a September 15 study start date.
Researchers will assign participants to receive either a low or high dose of oral CBD or a corresponding placebo. Those receiving CBD will take either 175 milligrams or 350 milligrams twice daily for between five and 56 days leading up to breast cancer surgery.
The unusual “window of opportunity” design allows researchers to examine tumor tissue after surgery and determine whether CBD use was associated with biological changes during the period between diagnosis and surgical treatment.
According to the Medical University of South Carolina, the study’s objective is to determine whether oral CBD produces changes related to cancer cell proliferation, using expression of the protein Ki67 as a marker. Researchers will also examine apoptosis, or programmed cell death, in the tumors.
The trial will separately track treatment-related adverse events and changes in anxiety using the Generalized Anxiety Disorder-7 questionnaire. Researchers are therefore examining both CBD’s potential effects on tumor biology and whether it affects anxiety during the waiting period before surgery.
Participants must be adults with stage I, II or III invasive breast cancer and a Ki67 proliferation rate of at least 10%. They must already be scheduled for surgery, with the operation taking place between five and 56 days after beginning the study treatment.
The study is being led by the Medical University of South Carolina and is currently recruiting at a single site in Charleston. The university previously received funding from Hollings Cancer Center for the Phase 1a CBD breast cancer trial.
The trial’s primary completion is currently estimated for March 2028, with overall study completion expected in March 2029.
Because the study is an early-stage clinical trial and has not yet produced results, it does not establish that CBD slows or treats breast cancer. Instead, researchers are testing whether administering CBD for a limited period before surgery produces detectable changes in the tumors themselves.
