Is it possible to fail to detect gastric cancer after ct with and without contrast/barium study, pet ct, cbc, metabolic testing, abdominal ultrasound, alpha feta protein, and flow cytometry? i also had egd and colonoscopy because of malignancy?

After so many neg. tests chances are0

No test can rule out cancers in extremely early stages. The work up you had is impressive and should give you peace of mind in ruling out gastric cancer in the current limits allowed by our understanding and current technology.

Why are you obsessed with stomach cancer. It is not that common in the US. The test are sufficient to rule out the cancer. You can reduce your risk of cancer by adopting healthy habits: Eat a mostly vegetarian diet, avoid alcohol, tobacco and street drugs, avoid excessive exposure to sun, get HPV vaccine, exercise 30 minutes each day, drink enough water so your urine is mostly colorless.