Each year, the San Antonio Breast Cancer Symposium (SABCS) brings together leading experts to share the latest breakthroughs in breast cancer research and treatment. At SABCS 2025, presentations by Dr. Louisa Lo highlighted important advances in HER2-positive breast cancer care, from improving treatment
for metastatic disease to refining early breast cancer therapy and using new technologies to personalise treatment.

Here’s what these findings could mean for patients and the future of breast cancer care.

Improving Treatment for Advanced HER2-positive Breast Cancer
One of the major studies presented was the HER2CLIMB-05 trial, which explored a new approach for people with HER2 positive metastatic breast cancer.

What was studied?
Researchers investigated whether adding the targeted therapy tucatinib to standard first-line treatment could help control cancer for longer after initial chemotherapy.
What did researchers find?
Tucatinib doubled the median duration of intracranial disease control when compared to placebo, when added to trastuzumab/ pertuzumab maintenance. Benefits were seen across different patient groups, including those with hormone receptor-negative disease. The group of interest here is the Her2 pos HR-ve group.
Why this matters?
This study suggests doctors may soon be able to strengthen first-line treatment for advanced HER2-positive breast cancer, potentially improving quality of life and delaying disease progression. It also supports a growing shift toward more targeted, chemotherapy-sparing treatment approaches.

Choosing the Best Hormone Therapy in Early HER2-positive Breast Cancer
Another key study discussed was the BIG 2-06 trial, which focused on people diagnosed with hormone receptor positive (HR+) and HER2-positive early breast cancer.
What was studied?
The research compared two common hormone therapy options used after initial treatment: Aromatase inhibitors, Tamoxifen
What did researchers find?
Aromatase inhibitors were associated with better long term disease-free survival.
Patients receiving aromatase inhibitors had a lower risk of recurrence over 10 years.
Overall survival was similar between treatments.
Why this matters?
These findings help guide doctors in choosing the most effective hormone therapy for this specific breast cancer subtype. Because HR+/HER2+ cancers are biologically complex, selecting the right therapy is important for reducing recurrence risk.

Using Blood Tests to Personalise Treatment (PHERGain study)
One of the most exciting areas of research presented involved circulating tumour DNA (ctDNA), tiny fragments of cancer DNA found in the bloodstream.
What was studied?
The PHERGain study examined whether ctDNA testing could predict how well patients respond to treatment in early HER2
positive breast cancer, compared with traditional imaging scans.
What did researchers find?
CtDNA clearance during or after neoadjuvant chemotherapy could potentially signal better breast cancer outcomes in early HER2- positive breast cancer.
Early PET imaging response and ctDNA clearance during neoadjuvant chemotherapy could potentially spare patients from chemotherapy after treatment with trastuzumab/pertuzumab. Although promising, these study findings will need to be confirmed in a larger randomised study for it to be practice changing.
Why this matters?
Blood-based monitoring could help personalise treatment decisions, potentially reducing unnecessary chemotherapy while ensuring high-risk patients receive more intensive care. This represents a major step toward truly personalised breast cancer treatment.

Advancing Care for HER2-Positive Metastatic Breast Cancer
BCRC-WA was proud to be part of the PATINA study, a large international clinical trial including 496 patients worldwide.
What was studied
The study focused on people living with ER-positive, HER2 positive metastatic breast cancer whose disease had not progressed following initial therapy. Researchers evaluated whether adding palbociclib to ongoing HER2-targeted therapy (trastuzumab and pertuzumab) plus endocrine therapy could improve disease control and patient outcomes.
What did researchers find
Progression-free survival median (PFS) increased by 15 months, from 29 months to 44 months. The risk of the cancer spreading to the brain was reduced. This approach represents the first routine use of CDK4/6 inhibitors in HER2-positive disease, building on their success in HR positive, HER2-negative breast cancer.
Why it matters
The results are practice-changing, offering a new, evidence-based treatment option for patients with HER2-positive metastatic breast cancer. Preventing brain metastases may improve both quality of life and survival. Findings highlight the critical role of clinical trials and patient participation in advancing breast cancer care and shaping future treatment guidelines.