Clinical spectrum and prognosis of follicular lymphoma with blastoid transformation: case series and a review of the literature.

Follicular lymphoma (FL) with blastoid transformation (FL-BT) is a rare entity. FL-BT has a dismal prognosis due to intrinsic biological characteristics, lack of evidence-based therapeutic guidelines, and exclusion from clinical trials. In order to understand the natural course of the disease and reconcile treatment strategies in patients with FL-BT, we reviewed available data. Thirty patients were identified, three from our institution (Roswell Park Cancer Institute) and 27 patients from peer-reviewed literature. Demographic, clinical, treatment, pathological, and cytogenetic characteristics were described. Most of the patients (90%) were treated with chemotherapy at transformation. Complete and partial responses to treatment were observed in 38.9% and 22.3% of the patients, respectively. The median overall survival for the entire group of patients was 11 months (range 0.8-30 months); half of the patients were found to have concurrent genetic alterations in the BCL-2 and C-MYC gene rearrangements (double hit). FL-BT with a double hit had a shorter median overall survival when compared to nondouble hit FL-BT (7 months vs. 26 months, respectively, P = 0.005). In our experience, FL-BT is a rare and grave clonal evolution in FL characterized by an aggressive clinical course, inferior response to standard chemoimmunotherapy, and poor clinical outcome. C-MYC rearrangements are common in FL-BT and may play a role in the progression from FL to FL-BT or the poor clinical outcomes observed. Periodic updates from academic institutions treating FL-BT may improve patient care.