Day 100 Absolute Monocyte / Lymphocyte Prognostic Score and Survival Post Autologous Peripheral Blood Hematopoietic Stem Cell Transplantation in Diffuse Large B-Cell Lymphoma

Day 100 prognostic factors post-autologous peripheral blood hematopoietic stem cell transplantation (APBHSCT) to predict clinical outcomes in diffuse large B-cell lymphoma (DLBCL) patients have not been studied. Thus, we retrospectively examined if day 100 absolute monocyte/lymphocyte prognostic score (AMLPS-100) affects clinical outcomes by landmark analysis from day 100 post-APBHSCT in DLBCL. Only DLBCL patients in complete remission at day 100 post-APBHSCT were evaluated. From 2000 to 2007, 134 consecutive DLBCL patients are qualified for the study. Patients with a day 100 absolute monocyte count (AMC-100) ≥ 630 cells/μL and day 100 absolute lymphocyte count (ALC-100) ≤ 1000 cells/μL experienced inferior overall survival (OS) and progression free survival (PFS). On multivariate analysis, the AMC-100 and ALC-100 remained independent predictors of OS and PFS. Combining both values into the AMLPS-100, the 5-year OS rates for low, intermediate, and high AMLPS-100 risk groups were 94% (95% CI, 83.0% 98.1%), 70% (95% CI, 58.6% 80.1%), and 13% (95% CI, 3.4% 40.5%), respectively; and the 5-year PFS rates were 87% (95% CI, 74.0% 94.1%), 68% (95% CI, 56.0% 77.8%), and 13% (95% CI, 3.4% 40.5%), respectively. The AMLPS-100 is a simple biomarker score that can stratify clinical outcomes from day 100 post-APBHSCT in DLBCL patients.


Introduction
Day 100 visit after stem cell transplantation is the current standard first follow-up visit to assess treatment response.Day 100 absolute lymphocyte count (ALC-100) [1], day 100 absolute monocyte count (AMC-100) [1], day 100 platelet count [2], graft versus host disease [3], and day 100 full donor chimerism [4] are day 100 prognostic factors related to clinical outcomes in allogeneic stem cell transplantation.In autologous peripheral blood hemato-poietic stem cell transplantation (APBHSCT), multiple myeloma documented minimal residual disease at day 100 was associated with inferior survival.Nevertheless, prognostic factors to assess prognosis for diffuse large B-cell lymphoma (DLBCL) patients achieving a complete remission at day 100 post-APBHSCT have not been evaluated.We previously reported that the absolute lymphocyte count (ALC) and absolute monocyte count (AMC) at diagnosis are independent predictors of overall survival (OS) and progression-free survival (PFS) in DLBCL [5].The combination of both biomarkers into the AMC/ ALC prognostic score (AMLPS) stratifies patients into three risk groups: low-(AMC < 630 cells/μL and ALC > 1000 cells/μL μL and ALC ≤ 1000 cells/μL) [5].The AMLPS has been recently validated in several independent studies [6,7] confirming its utility as an assessment tool of prognosis in DLBCL.Post-transplant immunologic reconstitution, particularly ALC recovery (ALC ≥ 500 cells/µL) at day 15, has also been associated with prolonged PFS and OS in multiple hematological malignancies [8][9][10][11][12][13][14][15][16][17][18][19] and solid tumors [20][21][22].However, recent reports suggest that the survival benefit obtained from early lymphocyte recovery poststem cell transplant in DLBCL patients could be lost with long-term follow-up [10].Therefore, the aim of this study was to evaluate if day 100 AMLPS (AMLPS-100) affects survival for DLBCL patients in complete remission at day 100 post-APBHSCT.The value of AMLPS-100 was also evaluated as a tool to identify high-risk patients for post-APBHSCT relapse that is simple and could be easily implemented in clinical practice.

Patient Population
DLBCL patients achieving complete remission at day 100 post-APBHSCT at Mayo Clinic, Rochester, MN between 2000 and 2007 were considered for this study.Patients transplanted with bone marrow or combined bone marrow and peripheral blood stem cells and patients with evidence of relapse or progression at day 100 post-APBHSCT were excluded.A total of 134 consecutive DLBCL patients in complete remission at day 100 post-APBHSCT qualified for the study.No patient refused authorization to use their medical records for research and none were lost to follow-up.Approval for the retrospective review of these patients' records was obtained from the Mayo Clinic Institutional Review Board and the research was conducted in accordance with US federal regulations and the Declaration of Helsinki.

End Points
The primary end point of the study was to assess the impact of AMLPS-100 on OS and PFS by landmark analysis from day 100 in DLBCL patients treated with APBHSCT.The AMC-100, ALC-100, and AMLPS-100 were obtained from a standard day 100 complete blood cell count (CBC).The secondary end point was to evaluate if the AMLPS-100 could stratify DLBCL patients into low-, intermediate-and high-risk groups for OS and PFS post-APBHSCT.

Response and Survival
Response criteria were based on the guidelines from the International Harmonization Project for Malignant Lymphoma [23].OS was measured from day 100 to the date of death, or last follow-up.PFS was defined as the time from day 100 to the time of progression, relapse, death, or last follow-up, whichever occurred first.

Statistical Analysis
OS and PFS were analyzed using the approach of Kaplan-Meier [24].Differences between the survival curves were tested for statistical significance using the 2-tailed log-rank test.The Cox proportional hazard model was used for the univariate and multivariate analysis to evaluate the impact of the variables listed under the prognostic factors section for OS and PFS times [25].The choice of the cut-off values for ALC-100 and AMC-100 was based on our previous AMLPS publication [5].χ 2 analysis was used to determine relationships between categorical variables.The Wilcoxon-rank test was used to determine associations between continuous variables and categories, and Spearman correlation coefficients were used to evaluate associations for continuous variables.All twosided p-values < 0.05 were determined to be statistically significant.

Patients' Characteristics
For this cohort of 134 DLBCL patients, the median age at day 100 post-APBHSCT was 57.5 years (range: 23 -77 years).Sixty-three percent of the patients were males, while 37% were females.The distribution of the patients' baseline characteristics at day 100 is included in Table 1.The median follow-up period from day 100 post-APBHSCT for the cohort was 5.5 years (range: 0.1 -12.7 years) and for living patients (N = 93) was 6.9 years (range: 2.5 -12.7 years).Twenty-seven patients died   Copyright

Day 100 AMLPS (AMLPS-100)
By univariate and multivariate analysis, the ALC-100 and AMC-100 were independent predictors for OS and PFS post-APBHSCT.Thus, we combinedALC-100 and AMC-100 into day 100 AMC/ALC prognostic score (AMLPS-100), using the same cut-off values from our previous publication of the AMLPS at diagnosis in DLBCL [5], to develop a simple scoring system that can be used to stratify by risk patients with DLBCL that are in complete disease remission at day 100 post-APBHSCT.

Discussion
Currently, there are no studies available to advise DLBCL patients in complete remission at day 100 post-APBHSCT of their long-term prognosis starting at day 100 post-APBHSCT.We previously published the AMLPS at diagnosis for DLBCL stratifies patients into three risk groups in regard to clinical outcomes.This AMLPS has been validated as an independent prognostic indicator in DLBCL patients by other independent groups [6,7].Hence, we sought to evaluate if the AMLPS-  100 retains its ability to predict clinical outcomes at day 100 post-APBHSCT making it a risk-assessing tool that could be used during follow-up of DLBCL patients in complete remission.
To support the hypothesis that the biomarker AMLPS-100 affects survival in DLBCL patients, it was necessary to demonstrate that both ALC-100 and AMC-100 were associated with clinical outcomes in DLBCL patients in complete remission at day 100 post-APBHSCT.We determined that DLBCL patients presenting with ALC-100 > 1000 cells/μL experienced significantly superior OS and PFS.Similarly, DLBCL patients with an AMC-100 < 630 cells/μL presented superior OS and PFS from day 100 post-APBHSCT.
Since both the ALC-100 and AMC-100 were independent predictors for OS and PFS, we combined them into AMLPS-100.The AMLPS-100 was able to stratify patients into low-, intermediate-, and high-risk groups for OS and PFS post-APBHSCT.
To minimize the inherent biases of a retrospective study, the following steps were taken.With regards to selection bias, we only included DLBCL patients that underwent APBHSCT.Patients infused with peripheral blood as well as bone marrow harvested stem cells were excluded.All patients were treated with the same conditioning regimen.All patients were required to be in complete remission at day 100 for the landmark analysis.With regards to confounding factors, our study included currently known prognostic factors, such as the IPI; in addition, we included Age-100, Hgb-100, ANC-100, LDH-100, WBC-100, and Plts-100, all of which have been reported as prognostic factors at day 100 post-allogeneic stem cell transplantation [1][2][3][4].
On the other hand, strengths of this study include the long follow-up period of a well-defined group of DLBCL patients in complete remission at day 100 post-APBHSCT, with a median follow-up from day 100 post-APBHSCT for the cohort of 5.5 years and 6.9 years for living patients.Secondly, AMLPS-100 combines clinical biomarkers for the host immunity (i.e., ALC) [5] and tumor microenvironment (i.e., AMC) [26,27].Thirdly, the AMLPS-100 is a simple biomarker score obtained from the day 100 CBC post-APBHSCT that can be used to assess clinical outcomes in DLBCL patients in complete remission at day 100 post-APBHSCT, whereas other prognostic techniques such as gene-expression profiling required fresh frozen tissue samples, limiting its use in complete remission DLBCL patients at day 100 post-APBHSCT.Further studies are warranted to validate the AMLPS-100.