Blood Drug Testing

What body/blood test is the best test for cancer in the body?

It seems these days that many ailments are misdiagnosed because something looks or feels like another ailment. My sister in law was diagnosed as having severe arthritis and told she had to "live with it"! 3 months later, after enterring a hospital she was diagnosed with stage IVb adenocarcinoma! What blood test should she have gotten to check for cancer before it reached this late stage so quickly after doctors had misdiagnosed this?

Public Comments

1. well, I don't know the answer, but will keep this open for others input because I would like to see the answer myself.
2. The CEA test. But good luck trying to convince a doctor to run one on you if you don't present with symptoms.