These categories should be applied to patients with ET and PV receiving disease-modifying therapies. The 3 categories of response should be used in a cumulative, sequential manner, starting from the clinicohematologic response (which represents the minimal set of criteria to be evaluated for assessing response). The decision to use a composite definition of response (clinicohematologic and molecular response, or clinicohematologic, molecular, and histologic response) will depend on the goal and expectations of therapy.