Imfinzi shifts gastric cancer treatment paradigm

Approval of chemo combination signals change in treatment pattern

Key endpoints improved… pCR tripled in Asian patients

With ‘Imfinzi’ receiving approval as a perioperative treatment for gastric cancer, there are signs that the immunotherapy-plus-chemotherapy strategy, which has long been established as the standard of care overseas, is set to gain full-scale traction in Korea as well.

On March 31, AstraZeneca Korea held a press conference at the Four Seasons Hotel in Seoul to share the significance of the expanded indication for Imfinzi (durvalumab) in gastric cancer and its clinical data.

On the 23rd, Imfinzi was approved as a perioperative treatment for patients with resectable gastric or gastroesophageal junction adenocarcinoma. The regimen involves combination therapy with FLOT chemotherapy (5-fluorouracil, leucovorin, oxaliplatin, and docetaxel) before surgery, followed by Imfinzi monotherapy as maintenance after surgery.

Do-Youn Oh, Professor of Hematology and Oncology at Seoul National University Hospital

With this approval, Imfinzi has become the first immuno-oncology drug approved in Korea for use in the perioperative treatment setting for gastric cancer.

Due to advanced screening systems and surgical techniques, the 5-year survival rate for gastric cancer patients in East Asia has been in the 75–80% range with postoperative adjuvant chemotherapy alone.

However, approximately 30–40% of stage III patients still experience recurrence, indicating persistent unmet needs.

Against this backdrop, perioperative treatment strategies involving chemotherapy before and after surgery have emerged as an alternative.

The goal of perioperative therapy is to eliminate micrometastases early and continuously suppress systemic disease thereafter.

In the U.S. and Europe, FLOT-based perioperative treatment has already become the standard. The addition of Imfinzi to this regimen has demonstrated significant clinical efficacy, supporting a shift in treatment patterns.

Do-Youn Oh, Professor of Hematology and Oncology at Seoul National University Hospital, said, “Perioperative strategies to improve resection rates are already standard overseas. The clinical benefits of combining immunotherapy with chemotherapy are clear.”

The Phase III MATTERHORN study was the basis for Imfinzi’s expanded indication. The trial was conducted on patients with stage II-III advanced gastric cancer who were candidates for curative surgery. While stage I gastric cancer has a high cure rate with surgery alone, stages II–III represent locally advanced disease with a higher risk of recurrence.

In this study, Imfinzi-based perioperative therapy showed a statistically significant improvement in overall survival (OS).

The efficacy of Imfinzi was consistently observed in Asian patients as well.

In an Asian subgroup analysis presented at ESMO Asia 2025, the Imfinzi plus FLOT combination demonstrated improvements in event-free survival (EFS), 3-year OS, and pathological complete response (pCR) compared to placebo plus FLOT.

At 24 months, the EFS rate was 72.1% in the Imfinzi group versus 64.2% in the placebo group. Median EFS was not reached in either group, suggesting potential widening of the gap with longer follow-up. OS also showed a similar improvement trend to that observed in global studies.

The improvement in pCR was particularly notable. In the Asian patient population, the pCR rate in the Imfinzi combination group was 18.9%, more than three times higher than the 5.6% in the placebo group.

Safety was also confirmed to be manageable compared to standard FLOT therapy. There were no significant differences between the two groups in Grade 3 or higher adverse events or treatment discontinuation rates, indicating that new safety concerns arising from the addition of an immunotherapy were limited.

On the 31st, AstraZeneca Korea held a press conference at the Four Seasons Hotel Seoul to explain changes in treatment strategies following the expansion of Imfinzi’s indication for gastric cancer.

Despite surgery remaining the cornerstone of gastric cancer treatment, there is growing recognition that surgery alone may not be sufficient for a cure. The MATTERHORN study suggests that combining immunotherapy and chemotherapy before surgery, followed by surgery and maintenance therapy, can improve long-term outcomes.

Professor Oh emphasized, “The proportion of patients completing postoperative Imfinzi adjuvant therapy was around 50%, which exceeded expectations. For patient groups at high risk of micrometastasis, it is important to determine treatment strategies by comprehensively considering various factors such as extensive lymph node involvement, T4 stage, and aggressive histological subtype.”

She added, “Clear criteria for determining which patients should undergo surgery first or receive neoadjuvant chemotherapy have not yet been established. Further discussion and accumulation of evidence are necessary to establish treatment strategies tailored to patient characteristics.”