My husband has essential thrombocythemia with calr mutation. his hematologist just changed his medication from hydroxurea to baby aspirin since december. his platelet count increased from 380 to 1118 within 6 months. would this be a safe treatment?

I'd be concerned about undertreatment in view of that high platelet count. Perhaps the hematologist is concerned about long term hydroxyurea causing leukemia. Hydroxyurea plus low dose aspirin is the extent of my experience but there are other treatment options. A consultation at a university hospital department of hematology would be worthwhile.