Advancements in HER2-Positive Breast Cancer Treatment

Scientists are intensifying efforts to identify reliable biomarkers that could help determine which patients with HER2-positive breast cancer might safely avoid chemotherapy before surgery, potentially sparing them from toxic side effects while maintaining effective cancer control.

The push comes as new data show that certain antibody-drug conjugates (ADCs), particularly trastuzumab deruxtecan, significantly improve outcomes in high-risk early-stage HER2-positive breast cancer when used after standard neoadjuvant therapy. Researchers hope these advances will allow more precise treatment selection, reducing overtreatment in patients who are likely to respond well to HER2-targeted therapies alone.

HER2-positive breast cancer, which accounts for about 15–20% of all breast cancer cases, tends to be more aggressive but also highly responsive to therapies targeting the HER2 protein. Traditionally, patients receive chemotherapy combined with HER2-targeted drugs before surgery—a approach known as neoadjuvant therapy—to shrink tumors and assess treatment response. However, not all patients benefit equally from chemotherapy, and many endure significant side effects such as fatigue, nausea, hair loss, and long-term risks like heart damage or secondary cancers.

Search for Biomarkers to Guide Treatment Decisions

A growing body of research focuses on identifying biological markers—such as specific gene expression patterns, protein levels, or immune signatures—that could predict which patients achieve a complete pathological response (meaning no detectable cancer remains at surgery) after HER2-targeted therapy alone. These biomarkers might help clinicians safely omit chemotherapy in low-risk cases while reserving it for those most likely to benefit.

Promising Role of Antibody-Drug Conjugates

Recent findings presented at major oncology conferences highlight the effectiveness of trastuzumab deruxtecan (T-DXd), an ADC that delivers chemotherapy directly to HER2-positive cancer cells. In the DESTINY-Breast05 trial, patients with high-risk early HER2-positive breast cancer who had residual disease after neoadjuvant chemotherapy and surgery showed significantly improved invasive disease-free survival when treated with T-DXd compared to trastuzumab emtansine (T-DM1), another ADC.

Specifically, after two years of follow-up, the T-DXd group had a 72% lower risk of disease recurrence or death compared to the T-DM1 group. These results led regulatory agencies to grant accelerated approval for T-DXd in this setting, underscoring its potential to improve outcomes even when initial treatment leaves behind microscopic disease.

Experts note that while these results are promising, T-DXd carries its own risks, including interstitial lung disease—a potentially serious inflammation of lung tissue—which requires careful monitoring. As such, identifying which patients truly need this intensified therapy remains critical.

Residual Disease and the Need for Precision

Another key area of investigation involves managing residual HER2-positive disease after neoadjuvant therapy with regimens like TCHP (docetaxel, carboplatin, trastuzumab, and pertuzumab). Studies show that even after such intensive pretreatment, some patients still have detectable cancer at surgery, indicating a higher risk of recurrence.

Researchers are exploring whether switching to ADCs like T-DXd in this setting can eliminate residual disease and improve long-term outcomes. Early data suggest that a significant proportion of patients achieve a pathological complete response when T-DXd is used after neoadjuvant therapy, although longer-term survival data are still needed.

The goal, according to oncologists involved in these studies, is not to escalate treatment indiscriminately but to use biomarker-guided strategies to escalate therapy only for those who need it while de-escalating or avoiding chemotherapy in patients who are likely to do well with HER2-targeted agents alone.

Challenges and Future Directions

Despite progress, no single biomarker has yet been validated for routine clinical use in deciding whether to omit chemotherapy in HER2-positive breast cancer. Challenges include tumor heterogeneity, dynamic changes in biomarker expression during treatment, and the need for standardized testing methods across laboratories.

Ongoing clinical trials, such as those investigating dual HER2 blockade with pertuzumab and trastuzumab without chemotherapy, are incorporating biomarker studies to better understand which patients can safely avoid chemo. Researchers emphasize that any shift toward chemo-free approaches must be grounded in robust evidence to avoid compromising cure rates.

For now, standard neoadjuvant regimens containing chemotherapy remain the backbone of treatment for most patients with HER2-positive breast cancer. However, the convergence of improved biomarker research and more effective targeted therapies like ADCs is paving the way toward increasingly personalized treatment strategies.