Lower leukemia relapse in pediatric patients with pulmonary cytolytic thrombi following allogeneic transplant

Pulmonary cytolytic thrombi (PCT) is an uncommon complication after hematopoietic cell transplantation. Although the pathogenesis is unknown, patients typically respond to systemic corticosteroid treatment. Considering corticosteroids may impair GVL reactions, we reviewed the records of 324 pediatric patients who received a transplant for leukemia and compared the outcomes of those with PCT (n=14) to those without PCT (n=310). PCT patients had a significantly more acute GVHD (aGVHD) and chronic GVHD (cGVHD). Though 3-year non-relapse mortality and OS were similar, there was significantly less relapse in patients with PCT compared to those without PCT (0 vs 28%, P=0.02), regardless of the presence or absence of aGVHD. In multivariate analysis, grade II-IV aGVHD (P=0.02), cGVHD (P=0.01) and development of PCT (P<0.01) were independently associated with less relapse. These data suggest that patients with PCT are at greater risk for GVHD, but at lower risk of leukemia relapse.