Gastric cancer is one of the leading causes of cancer-related deaths worldwide. One of the biggest challenges is that it is often diagnosed at a later stage, when it has already spread, making it harder to treat. Even when detected early enough for surgery, many patients face a high risk of their cancer coming back. Currently, chemotherapy before and after surgery (known as perioperative chemotherapy) is a standard treatment to reduce this risk. However, researchers are constantly looking for ways to improve outcomes.

The MATTERHORN Phase III clinical trial is a large, global study that investigated whether adding immunotherapy to standard chemotherapy before and after surgery could improve outcomes for patients with early-stage gastric or gastroesophageal junction (GEJ) cancer.

The study included 941 patients with early-stage, resectable (the tumour could be surgically removed) gastric or GEJ cancer, who were randomly assigned to receive either Standard chemotherapy before and after surgery, or Immunotherapy combined with chemotherapy before surgery, followed by more immunotherapy and chemotherapy after surgery.

The study goal was to see if adding immunotherapy — a treatment that helps the body’s immune system recognise and fight cancer — would improve the length of time a patient lives without the cancer progressing, coming back, or causing death, also known as event-free survival.

What Did the Results Show?

The results were highly encouraging, revealing that patients who received the immunotherapy-based combination had a 29% lower risk of their cancer progressing, returning, or causing death compared to those who received chemotherapy alone.

• These benefit was seen regardless of the level of PD-L1, a protein often used as a biomarker to predict response to immunotherapy.
• The combination treatment was well-tolerated, with no unexpected side effects. Safety results were consistent with what researchers had seen in earlier studies of the same therapies.
• The combination did not interfere with patients’ ability to undergo surgery — a critical part of treatment for early-stage gastric cancer.

These findings are significant for the gastric cancer community because they offer new evidence that combining immunotherapy with chemotherapy may be more effective than chemotherapy alone in preventing relapse in early-stage gastric cancer — a major step forward for patients and clinicians.

Why This Matters for Patients

For patients and families affected by gastric cancer, these results represent more than just statistics. They offer real hope for longer survival, lower chances of relapse, and a new standard of care that could become available in the coming years. While immunotherapy is already being used in some forms of advanced gastric cancer, this study extends its potential use to patients with earlier-stage disease, where the focus is not just on treatment but on curing the cancer and preventing it from coming back. Importantly, the treatment was shown to be effective across a broad range of patients, regardless of PD-L1 status. This means it could benefit a wide spectrum of individuals, not just those who test positive for a specific biomarker.

So What Happens Next?

These results are still under review by regulatory agencies and health authorities around the world. If approved, this combination approach could become a new standard of care for early-stage gastric and GEJ cancer in the near future.

In the meantime, the study findings will be presented to medical professionals and discussed by cancer societies to determine how best to integrate them into clinical guidelines.

Author:

Natasha Muench