Patients with spleen growth of greater than 25% based on an increase in spleen volume from Baseline were eligible for early unblinding, and for patients on placebo, cross over to ruxolitinib prior to the primary study endpoint being reached. If this spleen growth occurred before Week 24, it must have been accompanied by specific worsening of symptoms, based on worsening early satiety accompanied by weight loss or worsening pain requiring daily narcotic use. After Week 24, asymptomatic spleen growth alone was sufficient for early unblinding and potential cross over. Patients found to have been randomized to ruxolitinib after early unblinding prior to Week 24 were discontinued.