Sounds like this is nothing to worry about. You mght ask if an MRI or Ultrasound is of any benefit since others here seem to have had them in addition to CT...although you have essentially been watching them since '07.
Circulating tumor cell test might not help with this but I would be curious if your onc would do one anyway. Doesn't hurt to ask..even if inappropriate at this point...gets across your desire to be proactive.