Again, we're combining two different questions and the answers are not the same for both. It is not complicated at all, as you say. But combining the arguments is making it seem so.
1. Does the Her2 serum test "work" to monitor activity of Her2+ disease? Probably yes.
2. Is there any indication or recommendation to DO the the test (or any tumor marker or scan) after treatment for primary disease? No. Here are the NCCN guidelines on follow-up after primary disease:
Interval history and physical exam every 4-6 mo
for 5 y, then every 12 mo
Mammogram every 12 mo (and 6-12 mo post-RT
if breast conserved) (category 2B)
Women on tamoxifen: annual gynecologic
assessment every 12 mo if uterus present
Women on an aromatase inhibitor or who
experience ovarian failure secondary to
treatment should have monitoring of bone health
Assess and encourage adherence to adjuvant
hormonal therapy.
Sorry, it lost its formatting in the cut/paste. NCCN does not recommend any scanning or tumor marker testing because evidence shows that this is not of any benefit. I know it's counterintuitive to hear that there's no advantage to catching mets before there are symptoms. But that's what research shows. And you can probably think of examples, right on this list, that do support this information:
Think of women with widespread and urgently life-threatening mets who responded to treatment and had long periods of NED. Then there are those with initially small mets whose disease progressed relentlessly. Whether either of those women detected their mets a month or two earlier than symptoms would have arisen (because they were scanned or had markers done) would make no difference to outcome. They would not live longer (although they'd live longer with the knowledge of mets) nor would method or timing of detection affect their quality of life.
Oops, late for work. I have a little more to say and will try to get to it tomorrow, about uncertainty.....
Debbie Laxague