Japanese pharma giant Daiichi Sankyo has expeditiously altered the global guidelines for early-stage breast cancer by submitting a supplementary new medicine application to Japan's Ministry of Health, Labour, and Welfare, proposing the use of its blockbuster drug, Enhertu  in patients with HER2-positive disease shortly after surgery. The application followed late-stage study findings indicating that the drug reduced the risk of invasive cancer recurrence or death by 53% compared to the current standard treatment, trastuzumab emtansine (T-DM1). The decision marks a significant shift for ENHERTU—from extending life in advanced cancer to attempting to avoid relapse entirely in what doctors refer to as a "curative-intent" situation. 

The application is based on the findings from the worldwide phase 3 DESTINY-Breast05 trial, which were presented at the 2025 European Society of Medical Oncology Congress and then published in The New England Journal of Medicine. The experiment included 1,635 patients from Asia, Europe, North America, Oceania, and South America. All had HER2-positive early breast cancer but continued to have invasive disease despite having neoadjuvant therapy, which is treatment given before surgery to reduce the tumour. 

Simply put, they were patients whose cancer did not totally respond to initial medication treatment prior to surgery. Around half of such patients do not achieve what doctors call a "pathologic complete response", which means microscopic cancer cells persist. These remaining cells can grow back, increasing the likelihood of recurrence. 

In DESTINY-Breast05, Enhertu  reduced the chance of invasive illness recurring or causing mortality by 53% when compared to T-DM1. In cancer, where even a 20-30% improvement is regarded as notable, halving the risk of recurrence constitutes a significant clinical gain. 

"New adjuvant treatment options for breast cancer are needed to help reduce the likelihood of disease recurrence and improve long-term outcomes for more patients," stated Yuki Abe, PhD, Head of R&D Division in Japan and Head of Research at Daiichi Sankyo. "This submission demonstrates our commitment to bringing Enhertu  to patients in this curative-intent breast cancer setting." 

Adjuvant therapy is a treatment used after surgery to eliminate any leftover cancer cells that are too tiny to be detected by scans. This postoperative window is essential. When breast cancer spreads to distant organs, known as metastatic disease, the five-year survival rate drops dramatically from almost 90% in early-stage illness to roughly 30%. 

Daiichi Sankyo's decision to move Enhertu  "upstream" into early treatment not only increases the number of eligible patients but also attempts to halt progression before metastasis begins. Enhertu  is an antibody-drug combination, or targeted treatment, that combines a HER2-seeking antibody with a powerful chemotherapeutic payload. The antibody operates as a guided missile, connecting to cancer cells that overexpress the HER2 protein and delivering chemotherapy straight to them. This concept tries to improve precision while minimising damage to healthy cells. 

Globally, regulatory momentum is increasing. Enhertu  has already earned Breakthrough Therapy Designation from the U.S. Food and Drug Administration based on DESTINY-Breast05 results, and a submission is being reviewed in the European Union. Analysts consider the Japanese submission as part of a coordinated multinational effort to redefine treatment standards in major markets. 

Breast cancer remains the world's second most frequent malignancy, with over two million cases expected in 2022. Approximately one out of every five instances is HER2-positive, a subtype typically associated with more aggressive illness. For these patients, the idea of reducing relapse risk by more than half represents a significant change from managing recurrence to preventing it. 

If authorities accept the new indication, Enhertu  could soon become the new standard of care in early HER2-positive breast cancer, possibly changing the survival trajectory of thousands of women each year.