Citations

Abstract Glioblastoma (GBM) is the most common and lethal primary brain tumor, and novel therapeutic strategies that make a substantial impact on outcomes are sorely needed. Immunotherapies have shown great promise in the treatment of a number of cancers in recent year, and a concerted effort is being made to apply these treatment paradigms to GBM. However, many GBM patients exhibit profound immunosuppression, likely limiting the efficacy of such approaches. The mechanisms of this immunosuppression are poorly understood, but tumor-derived extracellular vesicles (EVs), may play a role. We demonstrate that GBM-derived EVs induce the development of myeloid-derived suppressor cells (MDSCs) and non-classical monocytes (NCMs). We further demonstrate that these EV-induced monocytic cells are immunosuppressive, resulting in impaired T cell proliferation upon co-culture. We found that the immunosuppressive effects of tumor-derived EVs appear to be driven by the induction of these immunosuppressive monocytes, as EV treatment of T cells did not significantly impact T cell proliferation. Further, we sought to characterize the important of programmed death ligand 1 (PD-L1) in the induction of these immunosuppressive monocyte populations. We found PD-L1 to be expressed in the EVs from GBM cell lines, and that modulation in PD-L1 expression via either constitutive overexpression or shRNA-mediated knockdown resulted in concordant changes in expression in tumor-derived EVs. We demonstrate that PD-L1 is important for the induction of NCM but not for MDSCs. Taken together, these findings point to a significant role for tumor-derived EVs in the induction of immunosuppressive monocytes in GBM, and that these cells may be a driving force of systemic immunosuppression. PD-L1 is one factor expressed in EVs that has immunomodulatory properties, but additional EV cargo likely plays a major role in the induction of immunosuppressive cells.

Abstract Introduction: Our group (Porrata et al, BBMT 2016; 22: 1017-1023) previously published that the infusion of autograft natural killer (NK) cells correlates with survival post-autologous stem cell transplantation (ASCT) in non-Hodgkin's lymphoma (NHL) patients. A limitation of our previous study was the lack of killer-immunoglobulin-like receptor (KIR) analysis. Thus, we set up to investigate if the infusion of autograft activating and inhibitory KIR affects survival in NHL. Methods: From December 2007 to October 2010, 122 NHL patients participated in our Phase III clinical trial. A total of 111 patients finished the trail and samples were available for analysis. We analyzed the content of the autograft for inhibitory and activating KIR using flow cytometry analysis of each apheresis collection. Overall survival (OS) and progression-free survival (PFS) were analyzed from the date of transplant. Results: With a median follow-up of 82.8 months (range: 2.1-122.3 months), patients infused with an activating NKp30 (CD158b-CD337+) KIR ≥ 0.09 x 109 cells/kg experienced superior OS and PFS vs < 0.09 x 109 cells/kg: [OS: median was not reached vs 39.8 months, 5 years OS rates of 95% (95%CI, 56%-98%) vs 43% (95%CI, 22%-48%), p < 0.0001, respectively; and PFS: median was not reached vs 12.7 months, 5-years PFS rates of 77% (95%CI, 65%-86%) vs 13% (95%CI, 6%-24%), p < 0.0001, respectively]. Patients infused with the inhibitory KIR2DL2 (CD158b+CD337-) KIR < 0.066 x 109 cells/kg experienced superior OS and PFS vs ≥ 0.066 x 109 cells/kg : [OS: median was not reached vs 48.2 months, 5 years OS rates of 86% (95%CI, 75%-93%) vs 44% (95%CI, 31%-88%), p < 0.0001, respectively; and PFS: median was not reached vs 25.6 months, 5-years PFS rates of 62% (95%CI, 49%-74%) vs 31% (95%CI, 20%-44%), p < 0.0002, respectively]. We combined NKp30 and KIR2DL2 into NKp30/KIR2DL2 ratio. Patients infused with an NKp30/KIR2DL2 ratio ≥ 1.8 experienced superior OS (Figure 1) and PFS (Figure 2) vs < 1.8 : [OS: median was not reached vs 33.4 months, 5 years OS rates of 95% (95%CI, 86%-98%) vs 33% (95%CI, 21%-47%), p < 0.0001, respectively; and PFS: median was not reached vs 14.9 months, 5-years PFS rates of 76% (95%CI, 63%-85%) vs 14% (95%CI, 7%-27%), p < 0.0001, respectively]. Multivariate analysis revealed that the NKp30/KIR2DL2 ratio was an independent predictor for OS [HR = 0.03, 95%CI 0f 0.01-0.07, p < 0.0001] and PFS [HR = 0.17, 95%CI 0f 0.09-0.31, p < 0.0001]. Conclusion: The NKp30/KIR2DL2 ratio provides a platform to develop an immunocompetent autograft to improve clinical outcomes in NHL patients undergoing ASCT. Figure 1. Figure 1. Disclosures Ansell: LAM Therapeutics: Research Funding; Bristol-Myers Squibb: Research Funding; Trillium: Research Funding; Affimed: Research Funding; Celldex: Research Funding; Takeda: Research Funding; Merck & Co: Research Funding; Pfizer: Research Funding; Seattle Genetics: Research Funding; Regeneron: Research Funding.

Abstract Abstract 2835 Background: Extrinsic growth and survival signals provided by nonneoplastic cells present within the tumor microenvironment promote the growth and survival of CLL cells. For example, bone marrow stromal cells, blood-derived “nurse-like” cells and follicular dendritic cells have been shown to promote the survival of CLL cells via the provision of both soluble and cell-contact dependent factors. More recently, monocytes were convincingly shown to support the survival of CLL cells during in vitro culture, and many of the factors (e.g. BLyS/BAFF, SDF-1, CD14) previously implicated in supporting the growth and survival of CLL cells are produced by monocytes. To explore the potential clinical implications of these in vitro findings, we evaluated the relationship between the absolute monocyte count (AMC) at diagnosis and disease progression in a well defined cohort of CLL patients. We hypothesized that the presence of a relative monocytosis at presentation in patients newly diagnosed with CLL may create a nurturing environment for CLL cells and be associated with more rapid disease progression. Methods: Previously untreated patients diagnosed with CLL/SLL within 12 months of presentation to the Mayo Clinic (from 1/1/2000-8/31/2010) were identified (n=1396). The AMC was obtained from routine complete blood counts (CBC) with automated or manual differentials that were performed within 3 months of diagnosis (n=947). The primary study objective was to determine whether the AMC is associated with time to first treatment (TTFT) in CLL. The secondary objective was to determine whether the AMC had independent prognostic value after adjusting for CD38/CD49d/Zap-70 expression, IGHV gene mutation status, and cytogenetic (11q-, 17p-) findings by FISH analysis. Results: The median age was 66 years and the median AMC was 550/μL (380–812/ μL, 1st-3rd quartile) at diagnosis (normal range: 300–900/μL). No significant difference in the median AMC was observed by age, gender; CD38, CD49d, or Zap-70 expression; IGHV gene mutation status or cytogenetic findings. Patients were followed for a median of 3.2 years (range: 0–10.3), with disease progression requiring the initiation of treatment observed in 268 (28%) patients. On multivariate analysis using a Cox proportional hazards model which incorporated age, gender and Rai stage, the AMC (as a continuous variable) was associated with TTFT with a hazard ratio (HR) of 1.099 (per unit change; 95% CI, 1.003–1.205; p=0.04). The optimal cutpoint for the association between AMC and TTFT was determined to be ≥1, 170/μL, a threshold that remained an independently significant predictor of TTFT after adjusting for age, gender and Rai stage with a HR of 5.1 (95% CI, 2.56–10.10, p<0.0001). The median TTFT was 1.0 year for patients with an AMC ≥1, 170/μL and 7.4 years for those with an AMC <1, 170/μL (p<0.0001). In order to evaluate whether the AMC had independent prognostic value after adjusting for other prognostic biomarkers, CD38, CD49d, Zap-70, IGHV gene mutation status and cytogenetic findings (11q- or 17p-), were individually incorporated into the multivariate analysis. In each case, the AMC remained an independent predictor of TTFT, with HRs ranging from 4.31 to 5.43 (p<0.0001 for all analyses). Conclusions: The AMC at the time of diagnosis as measured by a routine CBC is associated with accelerated disease progression in CLL/SLL independent of other prognostic biomarkers. These results suggest that the in vitro observation that nonneoplastic cells present in the tumor microenvironment promote CLL cell survival may have direct clinical implications for the prognostic evaluation of CLL patients and further substantiate the pathogenic role of monocytic cells in CLL. Disclosures: No relevant conflicts of interest to declare.

Abstract Background: The prognostic significance of lymphocyte counts and immune status has been carefully examined in lymphoid malignancies, but the importance of the lymphocyte count in chronic myeloid neoplasms is less clear. In a recent analysis of MDS cases associated with deletion of chromosome 5q (Holtan SG et al AmJHem 2008 Epub 12Jun), we observed that an ALC >1.2 × 109 cells/L at diagnosis is independently associated with improved survival. The prognostic value of ALC in MDS not associated with del(5q) is unknown. Methods: We reviewed the medical records of patients without del(5q) diagnosed with MDS at our institution over a 10-year period and gathered data on complete blood counts and leukocyte differentials, bone marrow findings, and clinical course. Inclusion criteria included diagnosis within 6 months prior to initial consultation at our institution and <20% marrow blasts. Patients were classified according to the International Prognostic Scoring System (IPSS) and the WHO-classification based Prognostic Scoring System (WPSS). Results: The median age of the 503 included patients (360 M, 143 F) was 69 years (range 20–91). Median follow-up was 14 months, and 65% of patients were known to have died with an overall median survival of 36 months. Cytogenetic results as classified by the IPSS were favorable in 326 (65%) patients, intermediate in 112 (22%), and poor in 65 (13%). Both IPSS and WPSS accurately stratified patients, but the WPSS was better at identifying the lowest and highest risk patients. Survival by IPSS risk group was as follows: low-risk disease (n=95, median survival 41.8 months), intermediate-1 (n=285, 23.6 months), 106 with intermediate-2 (n=106, 14.1 months), and high-risk (n=17, 8.05 months). WPSS risk groups included very low risk (n=87; median survival 71.9 months), low risk (n=149, 28.8 months), intermediate risk (n=85, 19.3 months), high risk (n=143, 14.4 months), and very high risk (n=39, 8.8 months). In univariate analysis, factors associated with poorer survival included advanced age (p = 0.0012), higher-risk WHO subtype (p<0.0001), increased marrow blast percentage (p<0.0001), poor-risk karyotype (p<0.0001), higher IPSS score or WPSS score (p<0.0001), lower hemoglobin (p<0.0001), lower MCV (p=0.03), lower ALC (p=0.001), and lower platelets (p=0.001). Factors not associated with survival included sex and ANC. In a multivariate model including only baseline CBC parameters, hemoglobin >10 g/dL (p < 0.001), MCV >96 fl (p = 0.0493), ALC >1.2 × 109/L (p = 0.0449), and platelet count >100 × 109/L (p = 0.0046) were associated with improved survival. A high baseline ALC also maintained independent prognostic significance in a multivariate model against the IPSS (RR 0.746, 95% CI: 0.598, 0.933, p = 0.0099), and the raw WPSS score (RR 0.791, 95% CI 0.633, 0.987, p=0.037) but not the WPSS group (p=0.0794). There was no significant difference in the distribution of IPSS scores between the ALC >1.2 × 109 cells/L and the ALC ≤ 1.2 × 109 cells/L groups, although there were significantly more WPSS high risk patients in the low baseline ALC group (p = 0.0163). The creation of an ALC-modified IPSS score by adding 0.5 point for an ALC ≤ 1.2 × 109 cells/L resulted in a significant increase in median overall survival of the low risk group (41.8 months versus 66.1 months, p < 0.001, Figure 1). Conclusion: ALC is a novel and easily obtained prognostic marker in MDS that provides information complementary to existing prognostic scoring systems. Figure 1. Kaplan-Meier curves based upon IPSS (a) and the ALC-modified IPSS (b), where 0.5 point was added for an ALC ≤ 1.2 × 109 cells/L. Figure 1. Kaplan-Meier curves based upon IPSS (a) and the ALC-modified IPSS (b), where 0.5 point was added for an ALC ≤ 1.2 × 109 cells/L.

Abstract The peripheral blood absolute lymphocyte count (ALC) on day 15 after autologous stem cell transplantation (ASCT) has been shown to be an independent predictor for overall survival (OS) for many malignancies including acute myelogenous leukemia (AML), breast cancer, multiple myeloma (MM), primary systemic amyloidosis, and Hodgkin’s and non-Hodgkin’s lymphoma (NHL). A recent report (Dean et al. BMT2005; 36, 1049–1052) suggested that infused autograft dendritic cells (DC) affect survival post-ASCT in NHL. Thus, DC recovery at day 15 post-ASCT was assessed and correlated with OS. Preliminary data from an ongoing prospective study of 28 NHL patients post-ASCT are reported. Absolute DC at day 15 was analyzed by four color flow cytometry using antibodies to CD3, CD14, CD16, and CD19. In this approach lymphocytes and DCs were initially gated by their similar forward and side light scatter characteristics; DCs were then identified as cells in this gate that lacked staining for the lymphocyte antigens CD3, CD16, and CD19 and the monocyte antigen CD14. The percentage of antigen negative cells cells in the lymphocyte gate was then multiplied by the coincident peripheral blood absolute lymphocyte to determine the absolute DC count. Survival was then analyzed using the Kaplan-Meier method. With a median follow-up of 18 months, patients recovering a DC of 10 cells/μl or above experienced superior median OS versus those who did not (not reached vs 21 months, p < 0.02, Figure 1). This study shows that an immunocompetent immune system at day 15 (not only ALC recovery, but also DC recovery) correlates with survival in NHL patients undergoing ASCT. Figure Figure

Abstract Abstract 85 Background: Follicular lymphoma (FL) is an indolent non-Hodgkin lymphoma (NHL) with a highly variable natural history. Clinical variables describing either patient- or tumor-specific characteristics, many of which are included in the Follicular Lymphoma International Prognostic Index (FLIPI), are used to risk-stratify patients at the time of diagnosis. However, characteristics of non-malignant cells present within the tumor microenvironment provide important prognostic information. For example, both immunohistochemistry and gene expression profiling studies demonstrate that lymphoma-associated macrophages (LAMs) are prognostically important in FL. As LAMs are monocyte-derived, we sought to determine whether the absolute monocyte count (AMC) obtained from a CBC at diagnosis is an adverse prognostic factor in FL. Methods: Consecutive patients with FL who were evaluated and treated at the Mayo Clinic, Rochester between 1998 and 2007 were considered for study participation. Study approval was granted by the Mayo Clinic Institutional Review Board. The primary objective of the study was to determine the significance of the AMC, obtained at the time of diagnosis from a standard complete blood count with differential, in predicting overall survival. The secondary study objective was to determine whether the AMC is an independently significant prognostic factor when compared with the FLIPI. Results: The median follow-up was 4.2 years (range: 2 months to 11 years) for the 355 patients included in this study. At diagnosis, 43%, 34% and approximately 23% of patients were classified as low-, intermediate- or high-risk by the FLIPI. The median AMC at diagnosis was 510/μL, with 8% of patients presenting with an absolute monocytosis. At diagnosis, 45% of patients were initially observed, 42% received combination chemotherapy or immunochemotherapy alone, while the remaining 13% underwent surgery or radiation. The AMC was evaluated as both a continuous and dichotomized variable on univariate analysis. The optimal cut-point for the AMC was determined to be 570/μL by ROC analysis and was used when analyzing the AMC as a dichotomized variable. A relative elevation in the AMC was associated with inferior overall survival, whether analyzed as a continuous or dichotomized variable, with hazard ratios (HR) of 1.002 (HR per unit change in AMC; 95% confidence interval 1.001–1.002; p=0.0002) and 3.4 (95% confidence interval 2.0–6.0; p<0.0001), respectively. The median OS for patients with an AMC <570/μL at diagnosis has not been reached, whereas a median OS of 10.2 years (95% confidence interval 7.8–11.2 years; p<0.0001) was observed for those patients with an AMC ≥570/μL. For comparison, median OS has not been reached for high-risk patients identified by the FLIPI. Among those patients who were initially observed, the median time to progression (TTP) was 31 months (95% confidence interval 25–37 months) for those with an AMC <570/μL at diagnosis. In contrast, patients with an AMC ≥570/μL experienced a significantly shorter TTP following initial observation, with a median TTP of 18 months (95% confidence interval 8–28 months; p=0.03). When adjusting for prognostic factors included in the FLIPI on multivariate analysis, the association between the AMC as a dichotomized variable and survival remained significant with a HR of 2.6 (95% confidence interval 1.5–4.6; p=0.001). When the FLIPI alone (high vs. low/intermediate) was analyzed on multivariate analysis, the AMC remained an independent predictor of survival (p<0.0001). Furthermore, the AMC provided additional prognostic information when superimposed upon the FLIPI. For example, a subset of patients classified as high-risk by the FLIPI were observed to have an OS comparable to low/intermediate risk patients identified by the FLIPI upon further risk-stratification by the AMC, with a 6-year OS of 80%. In contrast, high-risk FLIPI patients with an AMC ≥570/uL were observed to have a median OS of 4.2 years (95% confidence interval 2.7–7.2) and 6-year OS of 47%. Conclusions: The AMC is associated with overall survival in FL and is independent from the FLIPI on multivariate analysis. While the AMC did not appear inferior to the FLIPI in identifying high-risk patients, it may be most helpful when used in conjunction with the FLIPI. These results further support the central role of nonneoplastic myeloid-lineage cells in FL biology. Disclosures: No relevant conflicts of interest to declare.

Abstract The peripheral blood absolute lymphocyte count (ALC) post-autologous stem cell transplantation is an independent predictor for survival in non-Hodgkin’s lymphoma. The role of ALC recovery during and after standard CHOP chemotherapy for newly diagnosed diffuse large B cell lymphoma (DLBCL) has not been reported. We hypothesized that ALC recovery during/after CHOP chemotherapy has a direct impact on survival. 135 consecutive newly diagnosed patients with DLBCL treated with CHOP from 1994 through 2000 were retrospectively analyzed. The primary end point was to assess the role of ALC recovery during and after CHOP on progression-free survival (PFS) and overall survival (OS). The ALC recovery before each of the 6 cycles and at 3 months follow-up after completion of therapy were analyzed. Of the 135 patients, 41 patients received concomitant radiation therapy. The median age was 64 years (range: 21–83) and median follow-up was 46 months (range: 1–124). Superior OS and PFS were identified in patients achieving the ALC cut-off value that discriminated clinical outcomes at a high level of significance for blood counts obtained before cycles 1 (ALC ≥ 1.5 x 109/L, OS = not reached vs 54 months, p< 0.0048; PFS = not reached vs 23 months, p <0.0005), 2 (ALC ≥1.5 x 109/L, OS = not reached vs 59 months, p <0.0255; PFS = not reached vs 30 months, p <0.0082), 3(ALC ≥1.2 x 109/L, OS = not reached vs 59 months, p<0.0074; not reached vs 30 months, p <0.0060), and at 3 months (ALC ≥ 1.2 x 109/L, OS = not reached vs 60 months, p< 0.0080; PFS = not reached vs 42 months, p < 0.0017). Similar cut-off points for cycles 4 through 6 could not be identified. The ALC recovery between each cycles 1–3 and at 3 months were not independent of each other. Multivariate analysis demonstrated ALC for cycles 1–3 and at 3 months post CHOP to be independent prognostic factor for OS and PFS when compared to other significant prognostic factors including International Prognostic Index and radiation therapy. Patients were stratified into three groups based on whether or not they achieved cut-off values of ALC in the first 3 cycles: group I= ALC achieved in at least 2 of 3 cycles; group II= ALC achieved in only 1/3 cycles; and group III= ALC cut-off not achieved. A trend towards worse OS (p< 0.0035) (Figure 1) and PFS (p< 0.0003) was identified if patients did not achieve any of the cut-off values of ALC in the first 3 cycles. These data further support the hypothesis that there is a critical role of lymphocyte (immune) recovery during and after CHOP chemotherapy in DLBCL.

Abstract Peripheral blood infused total autograft absolute lymphocyte count (A-ALC) correlates with day 15 absolute lymphocyte count and is an independent prognostic factor for survival after autologous stem cell transplantation (ASCT) for non-Hodgkin lymphoma (NHL). Factors to enhance A-ALC collections are not well defined. We hypothesize that the number of peripheral blood apheresis collections (PBAC) directly correlates with A-ALC. 190 consecutive NHL patients who underwent ASCT at the Mayo Clinic between 1993 and 2001 were analyzed. The primary end point of the study was to assess the correlation between the number of PBAC and A-ALC. The secondary end point was to determine if the number of PBAC affected survival post-ASCT. Of the 190 patients, 18 patients underwent 1 PBAC, 23 patients 2 PBAC, 50 patients 3 PBAC, 37 patients 4 PBAC, 50 patients 5 PBAC, and 12 patients had ≥ 6 PBAC. There was no association between the number of PBAC and the number of CD34+ stem cells collected (p= 0.25). A strong association between number of PBAC and A-ALC (Kruskall Wallis test, p <0.0001)(Figure 1) was identified. Using a cut-off of 4 PBAC, superior overall survival (OS) and progression-free survival (PFS) were observed for patients that underwent 4 PBAC or more compared to patients that underwent less than 4 PBAC (86 months vs 18 months, p <0.0001; 76 months vs 10 months, p <0.0001, respectively). Multivariate analysis demonstrated PBAC ≥ 4 is an independent prognostic factor for OS (RR = 0.654, 95%CI: 0.529–0.804, p< 0.0001) and for PFS (RR = 0.682, 95%CI: 0.561–0.826, p< 0.0001) when compared with other significant factors including performance status, lactate dehydrogenase and extra nodal disease. These data suggest that increasing the number of PBAC beyond the minimum number required to meet CD34+ collection targets may result in improved overall and progression-free survival mediated by an increase in autograft absolute lymphocyte count.

Abstract Introduction: The immunoglobulin (Ig) is one of the most diverse molecules in nature, and its therapeutic potential, by stimulation of the immune system, has been widely studied/used. Its effect is manifest at the cellular and humoral compartments. However it is still to clarify the specific effect of each fraction of the molecule in the observed immune stimulation. Aims: To develop a murine model of ASCT that mimics the autologous transplant in humans To study the independent effect of the various fractions of the immunoglobulin in the reconstitution of the immune system after ASCT. Methods: In this study, we developed, de novo, a murine model of ASCT. Four groups of transplanted animals were established (weekly injections of: Ig (n=8) or Fab fragment (n=7) or Fc fragment (n=6) or saline (control, n=7)). The evolution of the immune reconstitution was monitored weekly and compared among groups by characterization of cellular fractions by flow cytometry, serum levels of Igs by ELISA and thymic function by quantification of TRECs (“T cell receptor excision circles”). The statistical analysis of the longitudinal data was performed by a linear-mixed effects model. Results: We determined that a regimen of daily injections of G-CSF for 4 consecutive days produces a degree of mobilization of hematopoietic stem cells adequate for a donors/recipient ratio of 9 to 7, and to a standard engraftment extent. Regarding the recovery of cellular sub-populations among groups, the major differences occur up to the 6th week (w) after ASCT. As soon as 2 w after ASCT the treated groups show higher counts of CD4+ T cells compared with control mice (p<0.05). The maximum number of CD4+ T lymphocytes was attained at 2 w after ASCT for mice treated with Fab and Fc and at 9 w for mice treated with polyclonal Ig and PBS. The recovery of CD4+ T lymphocytes in the treated groups was higher compared to control (p<0.001 for Fab, p<0.001 for Fc and p=0.001 for polyclonal Ig). For CD8+ T cells, the mice treated with Fc show, during all the follow up, superior values, being statistically significant when compared to PBS treated mice (p=0.003). The differences with the other groups vary with time. Regarding the recovery of CD19+ lymphocytes, the mice treated with Fab reveal, after the 7th w, superior counts compared to all the other groups (p<0.05). Treated groups (Fab and Fc) show higher values of serum IgM compared to control, as well as an earlier recovery of levels (p<0.05). In what concerns CD4+ naïve T cells, the group treated with polyclonal Ig shows an increased recovery during the first weeks of treatment compared with the other groups (p<0.05). Conclusions and Discussion: The early treatment with polyclonal Ig or its fragments is highly beneficial for the recovery of CD4 and CD8 T lymphocytes (earlier recovery and higher cell counts). After the 6th week after transplant there is a tendency for homeostasis. The increase of CD4+ naïve T cells with Ig treatment may well correspond to an increased thymopoiesis, as suggested by our previous studies.

Abstract Abstract 4359 Routine serial chimerism analysis after allogeneic stem cell transplantation (Allo-SCT) has been used as a risk factor for post-Allo-SCT cancer relapse. In non-Hodgkin lymphoma (NHL) patients treated with autologous peripheral blood hematopoietic stem cell transplantation (APHSCT), a specific predictor during routine follow-up that could be used to ascertain risk for post-APHSCT relapse has not been identified. Thus, we set out to investigate if absolute lymphocyte count (ALC) measured at post APHSCT follow-up could serve as a marker of post-APHSCT NHL relapse. ALC was obtained at the time of confirmed relapse at follow-up and at last no evidence of relapse follow-up. From 1993 until 2005, 269 patients treated with APHSCT for diffuse large B-cell lymphoma (DLBCL), were included in this study. Patients at last follow-up with no relapse (N=137) had a higher ALC compared with those with confirmed relapsed at follow-up post-APHSCT (N= 132) [median ALC x 109/L of 1.66 (range: 0.13-3.69) vs 0.71 (range: 0.03-4.75), p <0.0001, respectively]. ALC at follow-up was a strong predictor for relapse with an area under the curve (AUC) = 0.86 (p<0.0001). An ALC of 1.0 × 109/L was identified as the optimal cut-off point. An ALC < 1.0 × 109/L at the time of confirmed relapse had a positive predictive value of 89% and a positive likelihood ratio of 8.4 to predict relapse post-APHSCT. Patients with an ALC ≥ 1.0 × 109/L (N = 147) had a cumulative incidence of relapse of 19% versus 92% for patients with an ALC < 1.0 × 109/L (N = 122) (p<0.0001) at follow-up post-APHSCT. This study suggests that ALC at follow-up can be used as a marker to assess risk of DLBCL relapse during routine follow-up after APHSCT. Disclosures: No relevant conflicts of interest to declare.