Treatment Outcome in Patients with Primary or Secondary Transformed Indolent B-Cell Lymphomas

Histologic transformation (HT) of indolent B-cell lymphomas into an aggressive form can occur simultaneously (primary HT, pHT) or sequentially after a preceding diagnosis of indolent lymphoma (secondary HT, sHT). The clinical course after diagnosis of HT is variable.

To describe the outcome of treatment in pHT and sHT patients.

We retrospectively analyzed HT cases with an underlying follicular lymphoma, nodal marginal zone lymphoma, extranodal marginal zone lymphoma, lymphoplasmacytic lymphoma, or small lymphocytic lymphoma at our institution. Kaplan-Meier estimates were used to calculate progression-free survival (PFS) and overall survival (OS).

Ninety-two HT patients were identified, 38 with pHT and 54 with sHT. In sHT, time-to-transformation was not influenced by the preceding treatment strategy of the indolent lymphoma component. In pHT, median PFS was 61 months (95% CI 27-61), and OS was not reached. In sHT, median PFS and OS was 14 months (95% CI 9-32) and 42 months (95% CI 16-90), respectively. Significant differences between pHT and sHT in PFS (p = 0.002; Hazard ratio [HR] 2.30, 95% CI 1.36-3.91) and OS (p = 0.0001; HR 3.30, 95% CI 1.81-6.03) were observed. Response to treatment for transformation was highly prognostic of PFS and OS (p < 0.0001).

The outcome in pHT cases is favorable and signifi-cantly better than in sHT cases. Failure to achieve a remission after treatment for transformation confers a dismal pro-gnosis.