&gt; Serum nucleic acid sampling to screen for malignancies has a few problems. One issue is that it runs into the realities of Bayes theorem.<p>Which is that the occurrence of a genuine positive result is so rare that the false positives <i>vastly</i> outnumber the real positives unless your test is amazingly good.<p>And this is a bad thing when the interventions are as horrific as most of our current cancer treatments.<p>This is the reason for the recent recommendations for both breast and prostate cancers to reduce screening unless you have actual risk factors (family history, obesity, smoking, etc.)