How well a cancer treatment works in real patients with stomach cancer

This is a real-world study of trastuzumab deruxtecan, a targeted cancer medication designed to treat advanced stomach cancer. Researchers will follow patients who have already decided to take this medication as part of their regular medical care and will track how well it works and what side effects people experience. Unlike a typical research study, participants don't receive the drug from the study itself—instead, researchers collect information about their treatment as it happens in regular hospitals and clinics.

While this medication has shown promise in controlled clinical trials, doctors want to understand how it actually performs when used by real patients in everyday medical settings, where people may have other health conditions or take other medications that could affect results.