This New York Times article discusses some of the pitfalls of cancer screening:
A new study found that people spent an extra $1,000 or so on health care in the year after a test raised suspicions that later proved unfounded. "The key here is to make sure that people are considering all the possible benefits and harms" when they go for a screening test, especially one not recommended by health officials, said Jennifer Elston Lafata, director of the Center for Health Services Research at the Henry Ford Health System in Detroit. Ms. Lafata led the study, which was published in this month's issue of Cancer Epidemiology Biomarkers and Prevention, a journal of the American Association for Cancer Research.
In addition to the financial costs of working up false positive results, there can also be health risks- for example bleeding or infection as the result of a biopsy. Go ahead and get the recommended screening tests (for example, colonoscopy for those over fifty) but avoid the "full body scans".