Outcome of transformed follicular lymphoma worsens according to the timing of transformation and to the number of previous therapies. A retrospective multicenter study on behalf of Fondazione Italiana Linfomi (FIL).

Optimal treatment for transformed follicular lymphoma (tFL) is not fully defined. Clinical characteristics and treatments that impact on post-transformation outcome of 176 biopsy-proven tFL were analysed. Transformation occurred at initial diagnosis in 52% (Group 1) and after a FL diagnosis in 48% (Group 2). Five-year overall survival was 84% for Group 1 and 51% for Group 2 (P < 0·001). In Group 1, 5-year progression-free survival was superior after rituximab maintenance compared to observation only (94% vs. 53%, P = 0·024). In Group 2, an inverse trend was found between survival and both a higher number of pre-transformation treatment lines and a short time-to-transformation.