I've read about a very small percentage of people having excellent results with Pegasys (?) a "type" of interferon.
A few have seemingly had their platelet counts normalized.

I was corresponding with a woman in one of the trials of Pegasys at MD Anderson.
I have a friend who had really bad side effects from interferon and am reluctant to try it.

I wonder, too, if they actually had "essential", not reactive, thrombocytosis. If I remember correctly, the "remission" has been about 3 years, so far.