This has changed for me recently as I was previously having the markers every 3 weeks, but only get Zometa at 6 weeks now. Need the blood work before Zometa to check creatinine level before they can give it. Markers have been low and steady for over 2 years, so I feel ok with every 6 weeks now. CT Scan was more often as well, but it has been SO clean (NED) that we moved up to 6 months.
THE MAIN THING I want to say is that these tests DO NOT give me ANY sress now as I have been getting good results for over 2 years. I could be in for a rude surprise one of these times, but until then I live in confidence with my Herceptin and Zometa.