Transformed non-Hodgkin lymphoma in the rituximab era: analysis of the NCCN outcomes database.

Histological transformation (HT) is a major cause of morbidity and mortality in patients with indolent non-Hodgkin lymphoma (NHL). The multicentre National Cancer Comprehensive Network database for NHL provides a unique opportunity to investigate the natural history of HT in the rituximab era. 118 patients with biopsy-confirmed indolent lymphoma and subsequent biopsy-confirmed HT were identified. Treatments for HT included autologous stem-cell transplant (auto-SCT) (n = 50), allogeneic SCT (allo-SCT) (n = 18), and treatment without transplant (n = 50). The 2-year overall survival (OS) for the entire cohort was 68%. For auto-SCT patients aged ≤ 60 years (n = 24), the 2-year OS was 74%. For non-transplanted patients aged ≤ 60 years (n = 19), the 2-year OS was 59%. The 2-year OS of patients naïve to chemotherapy prior to HT was superior to patients who were exposed to chemotherapy prior to HT (100% vs. 35%, P = 0.03). In this largest prospective cohort of patients of strictly defined HT in the rituximab era, the natural history of HT appears more favourable than historical studies. Younger patients who were not exposed to chemotherapy prior to HT experienced a prolonged survival even without transplantation. This study serves as a benchmark for future trials of novel approaches for HT in the Rituximab era.