Prognostic significance of histologic grade and Ki-67 proliferation index in follicular lymphoma.

The prognostic value of histologic grading and the Ki-67 proliferation index in follicular lymphoma (FL) is controversial. This study investigated the clinical usefulness of these two factors in Asian FL patients. Four hundred and thirty-three patients diagnosed with FL were retrospectively reviewed with a median follow-up time of 47.0 months (range, 24.0-168.0). The 10-year overall survival (OS) rate and progression-free survival (PFS) rate were 91.0% and 47.1%, respectively. Grade 3B and grade 3B with diffuse large B cell lymphoma (DLBCL) showed a better PFS than grade 1-3A (P < 0.001), and similar findings were noted in patients who received rituximab-containing regimens (P = 0.002). In contrast, no significant differences in terms of OS or PFS were observed between grades 1-2 and 3A. In addition, patients with Ki-67 ≥ 30% had a significantly better PFS than patients with Ki-67 < 30% (P = 0.014), although the difference was eliminated in the multivariate analysis. Both grade and Ki-67 index had no impact on prognosis in patients who did not receive rituximab treatment. In conclusion, grade 3A is closely related to grade 1-2, as reflected by a similar indolent clinical course and a lower PFS rate than grade 3B/3B + DLBCL. In addition, a higher Ki-67 index seems to have a positive effect on PFS in FL patients.