The Number of CD4+ T-Lymphocytes in the Autograft Correlates with Outcome After Autologous Stem-Cell Transplantation in Relapsed Hodgkin Lymphoma and Diffuse Large B-Cell Lymphoma.

Abstract 3422

Poster Board III-310

Autologous stem-cell transplantation (ASCT) is the standard treatment for relapsed diffuse large B-cell lymphoma (DLBCL) and Hodgkin's lymphoma (HL). The absolute lymphocyte count (ALC) in the autograft has been shown to correlate with survival after ASCT for lymphomas, but which lymphocyte subset in the autograft is responsible for this effect remains unknown. The aim of the present study was to retrospectively evaluate the impact of the number of CD4+ and CD8+T-cells in the autograft on the outcomes of ASCT.

Patients with a diagnosis of relapsed HL or DLBCL submitted to an ASCT between 1999 and 2006 were included. Patients were excluded if a sample of the autograft was unavailable. No patient had HIV infection.

The mobilization scheme consisted of subcutaneous G-CSF in 70% of the patients. The remaining patients were given cyclophosphamide 1.5 g/m2 or 4g/m2 with G-CSF. The conditioning regimen was cyclophosphamide 6 g/m2, BCNU 300 mg/m2 and etoposide 1200 mg/m2 in all but two patients. Growth-factor support was started five days after the infusion. The ALC in the autograft was calculated as the lymphogate in the FACS analysis. T-cell count was calculated as the total number of CD3+ lymphocytes, and T-cell subsets were determined by the number of CD4+ or CD8+ cells in the autograft. The antibodies used in the FACS analysis were: anti- CD45-FITC (BD- PharMingen), anti- CD4-FITC/ CD8-PE/ CD3-PercP (BD- PharMingen) and anti- CD3-FITC (BD- PharMingen).

Among the 48 patients (34 with HL and 14 with DLBCL) available for study, the median age was 34 years (12-65), 37 were males (73%), and advanced stage disease (Ann Arbor stage III or IV) was present in 38 patients (75%). The number of previous treatments ranged from one to four, and radiotherapy had been given to 51% of the patients. The median time from diagnosis to the ASCT was 1.8 years (0.4 to 15.3). The median numbers of infused cells were mononuclear cells 5.7×108/kg (1-15), CD34+cells 4.1×106/kg (1.7-19.6) and lymphocytes 261/mm3 (23-978). The median numbers of T-cell subpopulations were CD3+ 164/mm3 (7-706), CD4+ 68/mm3 (3-284), CD8+ 75/mm3 (3-401), CD4-CD8- 9/mm3 (0.3-154) and CD4+CD8+ 1.3/mm3 (0.01-15). Those values were used as cutoffs for the lymphocyte count comparisons.

In univariate analysis, the mobilization scheme including chemotherapy was associated with a higher median number of collected CD34+ cells/Kg (8.0 vs 4.17, p= 0.003), with a lower median number of total lymphocytes (203 vs 372, p=0.003), CD3+ T-cells (144 vs 249, p=0.005), CD8+ T-cells (50 vs 114, p<0.001) and there was also a trend towards lower CD4+ T-cells (67 vs 102, p=0.09). There was no association between the CD4+ T-cell subgroups and the type of disease, time from diagnosis to transplant, number of days of apheresis, mobilization scheme, stage of disease, number of previous treatments, or CD34+ cell counts.

The median follow-up of the living patients was 1.9 years from the ASCT. Survival curves could be determined for 46 patients: 27 were alive, and 19 patients had died at the time of this analysis. In the univariate analysis, the type of disease, ALC, CD3+, CD4+, CD8+ and CD4+CD8+ T-cells had a statistically significant association with the 2-year overall survival (OS). The best discriminator of survival was the number of CD4+ T-cells (95% vs 43%, p<0.001). Both CD4+ and CD4+CD8+ T-cells were also associated with better event-free survival (EFS) (55% vs 19%, p=0.001, and 53% vs 24%, p=0.003, respectively).

Multivariate analyses of OS and EFS were performed, including the type of disease and the counts of CD4+ and CD4+CD8+ T-cells. Regarding OS, only CD4+ T-cells (HR 11.87, 95%CI 2.71-51.99, p=0.001) and disease type (HR 2.54, 95%CI 1.00-6.45, p=0.05) remained statistically significant. Regarding EFS, only CD4+ T-cells (HR 2.94, 95%CI 1.28-6.79, p=0.01) and CD4+CD8+ T-cells (HR 2.88, 95%CI 1.18-7.04, p=0.02) retained statistical significance.

If the findings in this study are confirmed, efforts should be made to collect sufficient numbers of CD4+ cells in every patient. A carefully designed prospective study is needed to address this issue, and to better define the various lymphocyte subpopulations involved in this phenomenon.