Key Takeaways
Dormant cancer cells can linger and cause cancer to return years later
A new clinical trial identified and targeted these cells in high-risk breast cancer survivors
The small trial showed a significantly lower-than-expected recurrence rate, offering new hope for prevention
FRIDAY, Oct. 24, 2025 (HealthDay News) — University of Pennsylvania researchers are charting a revolutionary course in cancer treatment, targeting hidden "sleeper cells" that cause breast cancer to return and spread years after the original tumor is removed.
The team, led by oncologist Dr. Angela DeMichele, has advanced a method to identify and attack these dormant cells. Called disseminated tumor cells or DTCs, they break away from the main tumor and lie undetected in areas such as the bone marrow.
The method was recently described in the journal Nature Medicine.
Standard practice is to wait for the cancer to visibly reappear in a new part of the body.
“The way that we follow patients, we are not going to, right now, find the cancer until it's already found its way to another part of the body, and by that time it's incurable,” DeMichele told CBS News. “So our goal was to find a way to identify the cells that actually were lurking.”
One participant in the trial, Illeana Casiano-Vazquez, was treated for triple-negative breast cancer, an aggressive cancer with high odds of recurrence.
Her chance of the cancer returning within five years was estimated at 25%.
After Casiano-Vazquez’s initial chemotherapy and double mastectomy, DeMichele's team found sleeper cells in her bone marrow. She was then given medications to eliminate these microscopic remnants.
DeMichele was pleased with the outcome, saying that after six months of treatments, doctors were “so thrilled we could no longer see these dormant cells in her bone marrow.”
The small Phase 1/2 trial included 51 women. They were followed for a median of three years, meaning half were followed longer, half for a shorter time.
Disease-free survival rates around the three-year mark were 91.7% for patients taking hydroxychloroquine; 92.9% for those taking everolimus; and 100% for those taking a combination of the two drugs.
Survival was most improved in patients whose sleeper cells cleared.
After a seven-year follow-up, two participants experienced a cancer recurrence — a rate far below what was statistically expected for this high-risk group, DeMichele said.
For patients like Casiano-Vazquez, this research provides vital reassurance.
“The mental struggle that comes with the fear of recurrence is real and strong,” she told CBS News. Now a part of a follow-up study, she holds onto the hope the research provides.
“The only chance I have is if this clinical trial continues to work," Casiano-Vazquez said. "It's a chance that other women have, to give them hope that it won't come back.”
Researchers now plan larger clinical trials to confirm their findings and explore whether this targeted approach can be applied to prevent recurrence in other types of cancer.
More information
The National Cancer Institute (NCI) provides information on new developments and clinical trials for breast cancer.
SOURCES: CBS News, Oct. 22, 2025; Nature Medicine, Sept. 2, 2025
What This Means For You
Future breast cancer treatment regimens may include tests and therapies specifically designed to eliminate dormant cancer cells to prevent relapse.
