Treatment decisions for stage I triple-negative breast cancer (TNBC), an aggressive breast cancer subtype, have historically relied on tumor size and lymph node involvement. However, researchers say those factors alone may not fully capture a patient’s risk of recurrence or clinical benefit from treatment.
During an educational session at the 2026 ASCO Annual Meeting, presenter Roberto Antonio Leon-Ferre, MD, a medical oncologist at Mayo Clinic’s Comprehensive Cancer Center, discussed the unique biological characteristics of stage I TNBC and the growing effort to identify better which patients may benefit from treatment escalation.
“Triple-negative breast cancer is a highly heterogeneous disease, and stage I is not an exception,” Dr. Leon-Ferre said during the presentation.
The presentation was part of a broader ASCO session examining current and future treatment approaches in TNBC, including advances in both early-stage and metastatic disease.
Although TNBC is often considered an aggressive form of breast cancer, researchers are recognizing that stage I disease can vary significantly from patient to patient due to its underlying biology. Some patients may face a higher risk of recurrence, while others may achieve favorable outcomes with less intensive therapy.
Dr. Leon-Ferre highlighted three patient cases who had similarly sized tumors but varying clinical characteristics, including differing ages, tumor grades, genetic mutations, immune activity, and tumor subtype. These differences may influence both prognosis and the potential benefit of systemic therapy.
“The absolute benefit of chemotherapy in stage I TNBC is highly variable, with some patients deriving more benefit,” Dr. Leon-Ferre said.
Although some patients may benefit from chemotherapy, others may only experience a small reduction in recurrence risk despite exposure to treatment-related side effects.
Many patients with stage I TNBC experience favorable outcomes, particularly those with smaller tumors.
Dr. Leon-Ferre cited retrospective data suggesting that patients with T1a and some T1b node-negative TNBC may have great outcomes regardless of whether they receive chemotherapy. Patients with T1c TNBC, however, appear more likely to benefit from systemic treatment.
Current clinical guidelines generally recommend:
Despite advances in precision oncology, treatment decisions remain largely based on tumor size and nodal status.
“Beyond tumor size and nodal status, we currently do not have any biomarkers to help us guide the intensity of systemic therapy,” Dr. Leon-Ferre said.
A major focus of ongoing stage I TNBC research is determining whether some patients can safely receive less intensive treatment without compromising outcomes.
Several studies have evaluated anthracycline-free chemotherapy treatment regimens, including combinations of taxanes and platinum agents. While results have varied, some trials have demonstrated outcomes comparable to traditional anthracycline-based approaches.
Other studies have explored combining immunotherapy with less intensive chemotherapy regimens. For example, Dr. Leon-Ferre discussed data from the NeoPACT Phase 2 clinical trial, which evaluated pembrolizumab plus carboplatin and docetaxel in patients with stage I-III TNBC. Among patients with node-negative disease, approximately two-thirds of patients achieved a pathologic complete response without receiving anthracycline chemotherapy.
“Balancing the risk of recurrence with the risk of the treatment toxicities themselves is critical,” Dr. Leon-Ferre said.
The majority of the presentation focused on the need for biomarkers that can identify which patients require more intensive treatment and which may be candidates for de-escalation. One of the most promising biomarkers is tumor-infiltrating lymphocytes (TILs), which measure immune activity within and around a tumor.
Dr. Leon-Ferre highlighted research showing that patients with stage I TNBC and high TIL counts experienced great clinical benefit, even without chemotherapy. Multiple prospective clinical trials are now evaluating whether TILs can guide treatment decisions.
Researchers are also studying:
Early data suggest these approaches may help predict recurrence risk, treatment response, and pathologic complete response rates, but further research and validation are necessary before implementation into routine clinical practice.
The presentation also highlighted emerging targeted treatment strategies for select patient populations.
For patients with germline BRCA mutations, researchers are evaluating whether PARP inhibitors, a class of targeted therapies, could potentially replace some chemotherapy.
Dr. Leon-Ferre discussed results from the OlympiA-related OlympiAN study, in which adjuvant olaparib produced complete response rates approaching 70 percent in certain patients with BRCA1 or BRCA2 mutations. Higher response rates were observed when olaparib was combined with immunotherapy in higher-risk patients.
These findings suggest that some patients may eventually become candidates for chemotherapy-free treatment approaches, though additional research is needed.
Dr. Leon-Ferre’s ASCO presentation underscored the growing complexity of treatment planning for stage I triple-negative breast cancer. As researchers continue exploring biomarkers and more personalized treatment strategies, clinicians are working toward a more individualized approach that better identifies which patients may benefit from treatment intensification.
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