2025 San Antonio Breast Cancer Symposium

2025 San Antonio Breast Cancer Symposium

The 2025 San Antonio Breast Cancer Symposium (SABCS) brought together researchers, clinicians, and consumers from around the world to share the latest advances in breast cancer research and care.

This year’s meeting highlighted important progress across the full spectrum of breast cancer – from earlier diagnosis and less invasive surgery, to more effective and better-tolerated treatments for both early and advanced disease. Several studies focused on personalising care, reducing unnecessary treatment, and improving quality of life, while others explored new therapies that can help people live longer with fewer side effects.

Below is a summary of research highlights from SABCS 2025.

Neo-N

The Neo-N clinical trial is an Australian study, that was coordinated by Breast Cancer Trials, and examined whether adding newer immunotherapy treatments to shorter duration chemotherapy before surgery, can safely and effectively treat early-stage triple negative breast cancer—an aggressive form of the disease.

This study found that a series of blood tests to detect ‘circulating tumour DNA’, could help inform the future of triple negative breast cancer treatment.

The tests look for tiny fragments of tumour DNA that have been released by the breast cancer into the blood. Researchers found that when this tumour DNA could not be detected during or after treatment, women were more likely to have no remaining signs of cancer at the time of surgery and had better long-term survival outcomes.

Currently, patients with early stage triple negative breast cancer often need long duration multi-agent chemoimmunotherapy, which can cause significant side effects. This study is exploring whether some of that chemotherapy can be safely replaced with immunotherapy while still achieving strong results for patients.

Study Chair Professor Sherene Loi explained that these results could mean a new horizon for triple negative breast cancer, which accounts for approximately 15% of all breast cancers diagnosed.

“Clearance of circulating tumour DNA indicates that the treatment on the tumour appears to be working and killing off the cancer,” explained Professor Loi. “Triple negative is a type of breast cancer that is lacking features we can target, unlike other breast cancer types, making it a difficult breast cancer to treat, so these latest results are an exciting breakthrough.”

The Neo-N trial recruited patients at 18 institutions in Australia and New Zealand, and an institution in Italy, with a total of 108 participants with triple negative breast cancer. The Study Chair was Professor Sherene Loi.

Click here for more information about Neo-N clinical trial results.

HER2CLIMB-05

This study focused on people with HER2-positive metastatic breast cancer receiving their first treatment. All participants had already completed initial chemotherapy and HER2-targeted treatment and their cancer had not worsened. Many had cancer that had spread to organs such as the liver or lungs, and about half also had hormone receptor–positive disease.

The study tested whether adding a drug called tucatinib to ongoing HER2-targeted treatment could delay cancer growth. The results were encouraging: people who received tucatinib lived almost nine months longer on average before their cancer progressed compared with standard treatment alone.

The benefit was seen across all groups, regardless of hormone receptor status. So far, there has been no clear evidence that tucatinib reduced the risk of cancer spreading to the brain compared with standard treatment, although follow-up is ongoing.

Side effects were generally manageable. While diarrhoea was common in both treatment groups, only a small number of people stopped treatment because of it, suggesting the drug is well tolerated.

Recent studies have also shown strong results from other treatment approaches in this setting, including combining hormone therapy with targeted drugs or using newer antibody-drug therapies. As a result, doctors and patients now have several effective options potentially available, however deciding which is best will remain a challenge until more data become available.

LidERA

LidERA is the first major study to show that a newer type of hormone therapy can work better than standard treatment, in people with early hormone receptor–positive breast cancer.

The drug tested, giredestrant, is a next-generation oral therapy that blocks and breaks down the oestrogen receptor, helping to stop cancer cells from growing. The study included people with a range of cancer stages, from lower to higher risk of recurrence.

After nearly three years of follow-up, giredestrant reduced the risk of cancer returning by a small but meaningful amount compared with standard hormone therapy. This improvement was seen consistently across different patient groups, including those with higher-risk disease. Importantly, more than 9 out of 10 people taking giredestrant were cancer-free three years after treatment.

Side effects were similar to standard therapy, but fewer people stopped the new treatment because of side effects, suggesting giredestrant may be easier to stay on long-term.

Better-tolerated hormone treatments are important because they can help people stay on therapy and reduce the chance of cancer returning. Questions remain about whether combining giredestrant with other targeted drugs would provide even greater benefit, and how affordable widespread use would be.

AXSANA

Surgery to remove lymph nodes from the armpit has traditionally been used to help stage breast cancer and reduce the risk of spread. However, less extensive surgery may be just as safe for many patients.

AXSANA studied people whose cancer initially involved lymph nodes but appeared to clear after chemotherapy given before surgery. The goal was to see whether less aggressive lymph node surgery could safely replace full removal of lymph nodes.

After three years of study follow-up, the risk of cancer returning in the armpit was extremely low (99%), regardless of how much surgery was performed. Most patients also received radiation to the lymph node area, which likely contributed to these excellent results.

People who had more extensive surgery tended to have more aggressive disease overall, explaining higher rates of cancer spread elsewhere in the body—but not higher lymph node recurrence.

Longer follow-up is still needed, but this study supports the growing move toward less invasive surgery when it is safe to do so.

BOOG 2013-08

This Dutch study looked at whether sentinel lymph node biopsy—a common surgical procedure—can be safely omitted in selected people with small, early-stage breast cancer and no signs of lymph node involvement.

Most participants in this study were older than 50 and had slow-growing, hormone-positive cancers. After five years, people who did not have the procedure had outcomes that were just as good as those who did, in terms of cancer returning in nearby lymph nodes. Earlier results had already shown that avoiding this surgery led to better quality of life.

These results support a less-is-more approach for carefully selected patients, although doctors may be cautious about applying this to younger people until more long-term data are available.

TROG 07.01

This Australian-led study examined whether giving extra radiation to the tumour site after standard breast radiation reduces the risk of cancer returning in people with ductal carcinoma in situ (DCIS) that is not considered to be at low risk of recurrence.

After 10 years, people who received the extra “boost” radiation had a lower chance of cancer returning, including fewer invasive cancers. This benefit was seen regardless of the radiation schedule used.

Overall survival was the same for both groups. The boost did lead to more side effects such as skin irritation and breast discomfort, but these were usually mild.

This is the first long-term randomised study showing that boost radiation benefits people under 50, or older people with higher-risk DCIS features.

Menopausal Hormone Therapy and the Risk of Breast Cancer in Women with a Pathogenic Variant in BRCA1 or BRCA2

People with BRCA1 or BRCA2 gene mutations face high risks of breast and ovarian cancer. Surgery to remove the ovaries reduces ovarian cancer risk but causes early menopause, which can have serious short- and long-term health effects.

This study looked at whether menopausal hormone therapy (MHT) is safe for these women without a past history of breast cancer, after either menopause or preventive surgery to remove their ovaries. Reassuringly, women who used oestrogen therapy did not have higher breast cancer rates—in fact, rates were lower compared with those who did not use hormones.

No increased risk was seen with combined oestrogen-progesterone therapy either. These findings support the safe use of MHT in women with BRCA mutations who are experiencing significant menopausal symptoms, helping improve quality of life, bone and cardiovascular health.

WISDOM

The WISDOM trial studied a new approach to breast cancer screening based on individual risk, rather than the same schedule for everyone.

Participants had their risk assessed using personal factors, breast density, and genetic testing. Screening frequency and age of commencement were then tailored accordingly.

This approach was at least as effective as annual screening and may even be better, with fewer advanced cancers diagnosed, fewer mammograms performed, and lower overall costs. Genetic testing through mailed saliva kits was widely accepted, identifying people at higher risk who would not have been identified based on family history alone. Analysis of cost were also favourable compared with standard screening.

While risk-based screening requires more effort from participants, it offers a promising and more personalised way to screen for breast cancer.

PREFER

PREFER focused on fertility preservation in younger people diagnosed with breast cancer who needed chemotherapy.

The study showed that ovarian stimulation and egg freezing did not increase the risk of cancer returning or affect survival. In fact, outcomes were slightly better in those who preserved fertility, especially in hormone-positive cancers, although this difference was not statistically definitive.

Most participants also received treatment to protect ovarian function during chemotherapy. These results provide strong reassurance that fertility preservation is safe and should be routinely offered to eligible patients.

EMBER-3

EMBER-3 studied treatments for people with advanced hormone-positive breast cancer, whose disease had developed resistance to standard hormone therapy.

A newer hormone therapy, imlunestrant, worked better than standard options at delaying cancer progression, particularly when combined with the targeted drug abemaciclib.

Overall survival results showed a trend toward benefit but did not meet strict statistical thresholds, requiring longer follow-up to make a definitive conclusion about survival. The findings highlight how treatment choices in this setting are becoming increasingly complex, with several effective options and no clear single best approach yet.

PATINA

The PATINA study focused on people with ER-positive, HER2-positive metastatic breast cancer whose disease had not worsened after initial treatment.

PATINA is an international clinical trial, which enrolled 496 patients worldwide, including 49 patients from Australia and New Zealand through Breast Cancer Trials. The Australian Study Chair of PATINA is Professor Elgene Lim.

Adding the drug palbociclib to ongoing HER2-targeted and hormone therapy significantly delayed cancer progression. This follow-up analysis showed that palbociclib also reduced the risk of cancer spreading to the brain.

Brain metastases can seriously affect quality and length of life. Preventing them is a major goal, even though modern treatments can control disease after it develops. These findings reinforce the value of palbociclib in this treatment setting.