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Background Proteasome inhibitors (PIs) are approved for treating newly diagnosed and relapsed multiple myeloma (MM) in Colombia. This propensity score matching (PSM) analysis using data from the real-world, was designed to establish the role PIs (bortezomib or carfilzomib) at first relapsed or refractory MM. The primary endpoint was overall response rate (ORR) and secondary endpoint included was overall survival (OS). Moreover, an analysis of OS was done regarding response attained. On Behalf of RENEHOC-GRIMMCO (Colombian Registry for Hemato-Oncological Diseases and Colombian Mieloma Múltiple study group). Methods PSM by nearest neighbor analysis to evaluate the role of PIs used at first relapse in multiple myeloma of patients belonging to RENEHOC registry, between 2010 and 2020. Results 390 patients were identified in the first relapse of the Colombian registry, 269 patients with PI and 121 patients without PI. One hundred and ten patients were included in each group after PSM. Patients were matched for age, ISS, extramedullary disease, and use of lenalidomide to define the influence of this immunomodulatory drug in the PI group. A difference was found in the use of lenalidomide because only 1 patient was treated with PI and lenalidomide concomitantly (0.91%) compared to 31 patients in the group without PI (28.18%), (p Regarding ORR, no differences were found between the 2 groups 38.18% in PIs vs 37.27% in non-PIs group (p = 0.801). A trend towards better OS was found in the PIs group with a median of 58 months versus 39 months (p = 0.179). Overall survival in patients who achieved at least PR was better compared to those who did not reach 79 months versus 32 months in non-responders (p = 0.0001). Conclusion In this study, we found that the use of PI has a tendency to improve overall survival in real-world in MM patients when used in the first relapse and that this effect could possibly be enhanced with the combination with lenalidomide. Regardless of the treatment used, better responses are associated with better survival. Figure 1 Figure 1. Disclosures Abello: Janssen: Honoraria; Amgen: Honoraria; Dr Reddy's: Research Funding. Sossa: Amgen: Research Funding.

Acute leukemia is a heterogeneous set of diseases affecting children and adults. Current prognostic factors are not accurate predictors of the clinical outcome of adult patients and the stratification of risk groups remains insufficient. For that reason, this study proposes a multifactorial analysis which integrates clinical parameters, ex vivo tumor characterization and behavioral in vivo analysis in zebrafish. This model represents a new approach to understand leukemic primary cells behavior and features associated with aggressiveness and metastatic potential. Xenotransplantation of primary samples from patients newly diagnosed with acute leukemia in zebrafish embryos at 48 hpf was used to asses survival rate, dissemination pattern, and metastatic potential. Seven samples from young adults classified in adverse, favorable or intermediate risk group were characterized. Tumor heterogeneity defined by Leukemic stem cell (LSC) proportion, was performed by metabolic and cell membrane biomarkers characterization. Thus, our work combines all these parameters with a robust quantification strategy that provides important information about leukemia biology, their relationship with specific niches and the existent inter and intra-tumor heterogeneity in acute leukemia. In regard to prognostic factors, leukemic stem cell proportion and Patient-derived xenografts (PDX) migration into zebrafish were the variables with highest weights for the prediction analysis. Higher ALDH activity, less differentiated cells and a broader and random migration pattern are related with worse clinical outcome after induction chemotherapy. This model also recapitulates multiple aspects of human acute leukemia and therefore is a promising tool to be employed not only for preclinical studies but also supposes a new tool with a higher resolution compared to traditional methods for an accurate stratification of patients into worse or favorable clinical outcome.

Background In plasma cell neoplasms, the percentage of plasma cells in bone marrow (PPCBM) is important for diagnosis and assessment of the treatment. This quantification is performed using bone marrow multiparameter flow cytometry (FC), aspirate smears (BMA) and biopsy. Differences among the percentage of infiltration detected by these techniques have been reported, which can be related to a heterogeneous pattern of infiltration of multiple myeloma (MM) or sample quality. However, a simultaneous evaluation of these three techniques has not been reported nor their ability to detect bone marrow involvement with high or low infiltration, associated with different stages of this disease. Purpose The aim of this study was to compare the results of PPCBM obtained by FC, BMA, and biopsy with CD138 immunohistochemistry (BMB) in different stages of the disease with high and low infiltration, and the ability of these techniques to correctly classify the disease. Methods Pathological studies of patients referred to Hospital Fundación Santa Fe, Colombia were reviewed between January 2015 and June 2018. The selection of patients was based on both, a diagnosis of plasma cell neoplasms, classified according to the International Myeloma Working Group criteria and the simultaneous use of FC by FACSCanto II flow cytometer (Infinicyt 2.0 software program), wright-stained aspirate smears and biopsy with CD138 immunohistochemistry in the detection. Descriptive analysis was performed and PPCBM was expressed as the mean± standard error of the mean (SEM). The Kruskal-Wallis test was used to compare the mean of PPCBM among the three methods. Lineal regression and Spearman´s coefficient were used to correlate the variables. Statistical association was considered significant for p values Results A total of 130 patients with plasma cells neoplasms were included in this study, 57 with newly diagnosed MM (N), 58 following therapy MM (F) and 15 MGUS patients. In the N patients, the mean of infiltration was 12.3% ±1.8, 30.3% ±3.4 and 52.2% ±3.74 detected by FC, BMA and BMB, respectively. The PPCBM detected by this three analysis were significantly different (p In the comparative analysis of the three methods in all patients, the highest infiltration was always detected by BMB, followed by BMA and finally by FC (p 0.8). Finally, given that there are important PPCBM such as ≥10 that allows establishing the diagnosis of MM or ≥60%, considered an MM definitive event, we found that 21% and 52% of cases assessed by BMA and FC had PPCBM Conclusion In the comparison of the PCBM was observed a high linear correlation between MFC, BMA, and BMB, although we found a differential behavior of these methods, depending on the level of tumor infiltration. High percentages of infiltration, such as newly diagnosed MM patients, the BMB detected significantly more PPCBM than the others two methods (1.7 to 4-fold compared to BMA and FC). This supports the systematic incorporation of BMB into the analysis of patients with suspected MM for allowing a proper classification of disease. With low percentages of infiltration, such as MGUS and following therapy patients, the difference of PPCBM between BMA and BMB was not significant. Although, FC detected the lowest percentage of infiltration, it known its high specificity to discriminate tumor and normal plasma cells, being in one of the most important analysis to monitor minimal residual. Disclosures No relevant conflicts of interest to declare.

We present the case of a patient with progressive Langerhans cell sarcoma whose cutaneous lesions and nodal masses were treated with palliative radiotherapy. Response to relatively low doses of radiotherapy was both good and sustained. We recommend a dose of 15–30Gy depending on treatment intention and volume of the lesions.