So in cases of gastric cancer caused by h. pylori, the h. pylori tends to still be present at the cancer stage. and a ubt would test for it.

Mix up: H pylori does not directly cause cancer; it has ben occasionally found in association with a relatively less aggressive form of gastric lymphoma. H pylori usually causes gastric ulcers and the UBTest can detect the presence of Helicobacter so that treatment can be initiated

Not necessarily: Once cancer has developed, H. pylori is sometimes but not always identified. In the process leading to cancer, H. pylori can cause the stomach lining to develop "protective" metaplasia, and H. pylori tend not to be present in metaplasia. Also, even if present, the UBT has limitations in identifying H. pylori if the patient has been treated with antibiotics, proton pump inhibitors, etc