Breast Cancer Experts Spotlight Practice-Informing and Thought-Provoking Data From ASCO 2026

Recent findings from the 2026 ASCO Annual Meeting highlight a significant shift in breast cancer care, emphasizing more precise targeted therapies and the potential to reduce unnecessary treatment intensity. Leading oncologists are reviewing data that could soon translate into new clinical standards for various stages of the disease.

New Frontiers in Targeted Therapy

The VIKTORIA-1 trial (Study 2) evaluated gedatolisib, a novel mTOR/PI3K inhibitor, in patients with hormone receptor-positive, HER2-negative, PIK3CA-mutant advanced breast cancer. The study found that a gedatolisib-based triplet significantly improved progression-free survival (PFS) compared to the standard alpelisib plus fulvestrant.

Patients receiving the gedatolisib-based triplet achieved a median PFS of 11.1 months, while the control arm saw a median PFS of 5.6 months. While the agent is likely to get approved, experts note concerns regarding toxicity, specifically stomatitis, and its intravenous administration schedule.

Did You Know? The gedatolisib formulation is administered intravenously on a cycle of three weeks on and one week off.

the SERENA-6 trial focused on patients with ER-positive, HER2-negative advanced breast cancer who developed emergent ESR1 mutations. Switching to camizestrant while continuing a CDK4/6 inhibitor showed a significant benefit in time to second progression (PFS2).

The camizestrant arm achieved a median PFS2 of 25.7 months, compared to 19.1 months in the control arm. These findings provide thought-provoking data for the post-CDK4/6 inhibitor setting.

Reducing Treatment Intensity and Toxicity

Efforts to “de-escalate” treatment—reducing the amount of chemotherapy or surgery without sacrificing outcomes—are showing promise. The OPTIMA trial tested the 50-gene Prosigna assay to guide adjuvant treatment in high-risk ER-positive, HER2-negative early breast cancer.

Breast Cancer Highlights from ASCO 2026

The trial found that test-directed treatment was noninferior to the standard approach of chemotherapy followed by endocrine therapy. The 5-year invasive breast cancer-free survival rate was 90.3% in the test-directed arm versus 91.8% in the control arm.

Expert Insight: The convergence of the OPTIMA and SENOMAC trials suggests a paradigm shift where clinicians may be able to provide significantly less treatment for many patients while achieving the same clinical results.

Similarly, the SENOMAC trial examined the omission of complete axillary dissection in patients with one to two sentinel lymph node macrometastases. The results indicated that omitting the dissection did not worsen survival outcomes or relapse rates.

The 5-year overall survival rate for patients who omitted complete axillary lymph node dissection was 94.4%, compared to 93.4% for those who underwent the procedure. Experts suggest this could change how surgeons operate and should potentially become the standard of care.

Advancements in Triple-Negative Breast Cancer

For patients with previously untreated metastatic triple-negative breast cancer (mTNBC) who are not candidates for PD-(L)1 inhibition, the ASCENT-03 trial offered new insights. A post hoc analysis revealed that first-line treatment with sacituzumab govitecan (Trodelvy) significantly extended median PFS2 compared with standard chemotherapy.

Despite a lack of overall survival benefit in initial data, the PFS2 advantage suggests that sacituzumab govitecan could potentially be moved to earlier lines of treatment.

What May Happen Next

As these trials conclude, the medical community may see a shift toward more personalized chemotherapy schedules based on genomic assays like PAM50. If data are confirmed with longer follow-up, doctors may be able to avoid unnecessary chemotherapy for younger patients and those with multiple positive nodes.

the approval of gedatolisib could provide more options for patients with PIK3CA mutations, provided that toxicity issues are managed. Surgeons may also begin to more frequently omit complete axillary dissections in specific patient populations to reduce morbidity.

Frequently Asked Questions

What is the Prosigna assay used for in the OPTIMA trial?
It is a 50-gene genomic assay used to identify patients with high-risk ER-positive, HER2-negative early breast cancer who may not receive a meaningful survival benefit from adjuvant chemotherapy.

How did the SENOMAC trial affect the view on axillary dissection?
The trial showed that omitting complete axillary dissection in patients with 1 to 2 sentinel lymph node macrometastases did not worsen relapse rates or overall survival, suggesting it could become the standard of care.

What was the primary benefit of camizestrant in the SERENA-6 trial?
Camizestrant significantly improved the median time to second progression (PFS2) to 25.7 months compared to 19.1 months for those continuing standard aromatase inhibition in patients with emergent ESR1 mutations.

How do you feel about the move toward using genomic testing to reduce the use of chemotherapy in cancer treatment?