Peripheral Blood Involvement By Flow Cytometry As a Prognostic Factor in Aggressive T Cell Lymphomas Following Autologous Stem Cell Transplantation

Introduction: Aggressive T cell lymphomas (TCL) are a heterogenous group of lymphomas that are frequently associated with poor outcomes. Autologous stem cell transplantation (ASCT) is recommended according to the NCCN guidelines and by practice standards for most subtypes as a consolidation for patients in first remission. A large prospective study of up-front ASCT by the Nordic Lymphoma group identified age, ECOG performance status <2, and bone marrow involvement as important prognostic factors. We have identified peripheral blood involvement by flow cytometry at diagnosis in up to one third of patients with aggressive TCL and analyzed whether this was a prognostic factor for outcomes after ASCT.

Methods: We retrospectively analyzed data from consecutively treated patients (pts) with aggressive T-cell lymphomas who underwent ASCT at our institution from July 2009 to February 2019. Patient and disease characteristics were summarized using descriptive statistics. Kaplan-Meier analysis was used to estimate progression free survival (PFS) that was defined as the time from SCT to the first evidence of recurrence, and overall survival (OS) that was defined as the time from SCT to death or last institutional follow up with a hematologist. We collected data on age, co-morbidities, disease subtype, stage, response to therapy and treatment both pre and post SCT. Flow cytometry was obtained at diagnosis and phenotype of atypical circulating cells was compared with immunophenotype from tumor biopsy specimens.

Results: 50 pts with TCL who received ASCT were identified for this analysis. Of this population, 41 (80%) of pts had peripheral blood flow available at the time of initial diagnosis. T-cell lymphoma types included peripheral T cell lymphoma not otherwise specified (PTCL NOS, 17 pts), angioimmunoblastic T cell lymphoma (AITCL, 15pts), ALK negative anaplastic large cell lymphoma (ALCL, 1pt), enteropathy-type T-cell lymphoma (EATL, 2pts), extranodal natural killer T-cell lymphoma (NKTCL, 2pts) and panniculitis like T cell lymphoma (2 pts) (Table 1). Median age of the cohort was 62 years (range 20-75 years) and all patients included had an ECOG PS 0-1 at the time of diagnosis. The majority had stage 4 disease (36/41, 87.8%), but analysis included a small number of patients with stage 2 (1/41, 2.4%) and stage 3 (4/41,9.7%) disease. Bone marrow involvement by morphologic criteria was noted on bone marrow biopsy in 8/41 (19.5%) pts; bone marrow was negative in 28/41 or 61% pts and not evaluated in 8/41 or 19.5% pts. Flow cytometry of peripheral blood performed as part of initial staging was positive for circulating malignant cells in 13/41 pts (31.7%) at the time of diagnosis. All patients underwent ASCT in first remission. The median PFS and OS were 15.2 and 29.9 months respectively in the flow positive group, while neither median PFS nor OS were reached in the flow negative group (Figures 1 and 2). Flow cytometry results from time of diagnosis was not strongly associated with PFS (log rank, p = 0.39), however, it was associated with overall survival (log rank, p = 0.012). There were 11 deaths in the cohort- 4 in the flow negative group and 7 in the flow positive group. Further, when bone marrow involvement was evaluated, 7 of 13 pts with positive flow cytometry (53.8%) and 5 of 28 (17.8%) pts with negative flow cytometry had BM involvement, suggesting a correlation between positive bone marrow and detection of lymphoma cells in the peripheral blood at the time of diagnosis.

Conclusions: We demonstrate in our cohort of patients that detection of circulating lymphoma cells at diagnosis by flow cytometry was associated with a worse outcome in patients with aggressive T cell lymphomas undergoing ASCT as a consolidation in first remission. Larger cohorts will be needed to validate these findings, but these results suggest peripheral blood involvement by sensitive flow cytometry may identify patients with worse outcomes who might benefit from a more aggressive strategy such as allogeneic stem cell transplantation or alternative consolidation strategies.

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