Can you get a physical every year and still have undetected illnesses like cancer?

ABSOLUTELY!: Yearly physicals are a terrific tool for overall wellness. However, yearly physicals are only a part of your overall healthcare regimen. If you're a smoker, drink too much alcohol, eat too much fat, sodium, etc, then tell your md who will probably monitor your health in additional ways with screenings and radiographs/ct, etc to augment the yearly physical. In short, be honest and stay in contro.

Physical every year: Unfortunately the answer is yes. Many cancers can grow from undetectable to detectable in less than a year. This is why it is your job to examine yourself and listen to your body, watching for changes and new symptoms. If anything lasts more than two weeks consider visiting with your doctor.