ASCO Data Shows New Therapy Delays Breast Cancer Progression and May Improve Quality of Life for Women with Hormone Receptor-Positive Disease
Black women diagnosed with estrogen receptor-positive (ER-positive) breast cancer—a subtype that makes up the majority of breast cancer cases—face a sobering reality: despite receiving similar treatments as white women, they are 42 percent more likely to die from the disease. This startling gap, reported by BreastCancer.org, highlights a pressing need to improve how we diagnose and treat ER-positive breast cancer across all populations.
Several factors may be driving this disparity. Studies suggest that tumors in Black women are often higher grade and less responsive to hormone therapy. Others point to lower uptake of critical diagnostic tools like the Oncotype DX (OncoDx) test, which guides treatment decisions. Socioeconomic challenges and unequal access to care also continue to influence outcomes.
But research presented at this year’s American Society of Clinical Oncology (ASCO) Annual Meeting could change the future for many women living with this disease. One standout trial, SERENA-6, tested a strategy to catch treatment resistance early, before cancer begins to grow, and switch therapy in time to stay ahead of the disease.
What Is the SERENA-6 Trial?
In simple terms, SERENA-6 asked:
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Can we detect when a cancer is starting to resist treatment, before it grows, and switch drugs early to keep the cancer in check longer?
The trial involved women with metastatic hormone receptor-positive breast cancer who had been stable for at least six months on standard therapy: an aromatase inhibitor (AI) plus a CDK4/6 inhibitor (a targeted drug that helps stop cancer cells from dividing). Every few months, their blood was tested for signs of a genetic change called the ESR1 mutation, which signals that cancer may be preparing to resist hormone therapy.
“This mutation doesn’t show up at diagnosis—it develops over time as the cancer adapts to treatment,” Dr. Hope Rugo, Medical Oncologist at City of Hope, tells BlackDoctor.org. “We wanted to know: if we catch that mutation early, can we switch therapy and get ahead of it?”
What Did the Trial Find?
Out of 3,200 women enrolled, about 500 developed the ESR1 mutation. From this group, 315 were randomized: half stayed on their current treatment, and half switched to a newer hormone drug called camizestrant, an oral SERD (selective estrogen receptor degrader) designed to work even when this mutation is present.
The results were significant.
Women who switched to camizestrant had longer control of their cancer—about 16 months compared to nine months for those who didn’t switch. And perhaps even more important, they maintained a better quality of life.
“This is the first trial of its kind to show that we can act on early resistance before the cancer visibly grows,” Dr. Rugo says. “It’s a smarter, more proactive approach to treatment.”
Side effects were minimal. A few people experienced brief flickering lights when going from light to dark, but otherwise, the treatment was well tolerated. All patients continued their CDK4/6 inhibitor as part of the therapy.
Why This Matters
Camizestrant is not yet FDA-approved, and we still don’t know how it performs when given after cancer has already started growing—this wasn’t tested. But the takeaway is clear: monitoring for molecular changes and adjusting treatment before visible progression may offer women a better shot at longer disease control and better day-to-day living.
It’s a shift in strategy that could be particularly valuable for patients at higher risk of poor outcomes, including Black women, who may benefit from earlier and more personalized treatment adjustments.
“This is personalized cancer care in action,” Dr. Rugo adds. “We’re not waiting for the tumor to win the race—we’re trying to outrun it.”
What Else Is New? Other ASCO Highlights in Breast Cancer
ASCO 2025 featured several important trials that could reshape breast cancer treatment:
VERITAC-2: An Oral Option That May Be Better Than Injections
This study tested the oral drug vepdegestrant against the injectable SERD fulvestrant in women with metastatic ER-positive breast cancer. For patients with the ESR1 mutation, vepdegestrant worked better and was easier to take—a daily pill versus two monthly shots.
“This could be a game-changer in convenience without sacrificing effectiveness,” Dr. Rugo notes.
ASCENT-04: A New Combo for Triple-Negative Breast Cancer
Triple-negative breast cancer (TNBC) is notoriously hard to treat. The ASCENT-04 trial found that combining sacituzumab govitecan (SG) with immunotherapy drug pembrolizumab led to better disease control than standard chemotherapy plus immunotherapy.
“TNBC patients often have limited options. This trial gives them a more effective and less toxic choice,” Dr. Rugo says.
DESTINY-Breast09: Raising the Bar for HER2-Positive Breast Cancer
This study compared traditional chemo with HER2-targeted therapy to a newer option: trastuzumab deruxtecan (T-DXd) plus pertuzumab. The results were striking—patients had better cancer shrinkage and longer disease control with the newer approach.
However, lung inflammation occurred in about 10 percent of patients, and two died from it. Screening and early treatment are now key parts of managing this risk.
Advice for Patients Navigating These Results
New research is exciting—but it can also be confusing. Here’s what Dr. Rugo advises:
- Ask about molecular testing. Knowing if your cancer has mutations like ESR1 can open doors to different therapies.
- Explore clinical trials. Today’s breakthroughs came from patients who participated in trials like SERENA-6.
- Keep asking questions. Your care team can help interpret how new findings may apply to you.
To learn more, patients and caregivers are invited to the City of Hope® Breast Cancer Forum—a free online event moderated by Dr. Rugo on Monday, June 16 at 5 p.m. PT
Hope S. Rugo, M.D. is director of the City of Hope® Women’s Cancers Program and professor in the Department of Medical Oncology & Therapeutics Research. A global leader in breast cancer care, she has led clinical trials that aim to improve outcomes while reducing toxicity and improving patients’ quality of life.
