Advancements in minimal residual disease detection: a practical approach using single-cell droplet PCR for comprehensive monitoring in hematological malignancy.

The identification of chromosomal abnormalities accompanied by copy number alterations is important for understanding tumor characteristics. Testing methodologies for copy number abnormality have limited sensitivity, resulting in their use only for the sample provided at the time of diagnosis or recurrence of malignancy, but not for the monitoring of minimal residual disease (MRD) during and after therapy. We developped the "DimShift" technology which enable to measure the copy number of target gene/chromosome in each cell, which is given by the single cell droplet PCR. Qualitative result of DimShift given by peripheral blood was perfectly concordant with that of bone marrow. These findings and performances are promising to be the new methodology for MRD detection in malignant diseases utilizing bone marrow as well as peripheral blood.

Clostridium butyricum MIYAIRI 588 contributes to the maintenance of intestinal microbiota diversity early after haematopoietic cell transplantation.

In patients undergoing haematopoietic stem-cell transplantation (HSCT), the intestinal microbiota plays an important role in prognosis, transplant outcome, and complications such as graft-versus-host disease (GVHD). Our prior research revealed that patients undergoing HSCT substantially differed from healthy controls. In this retrospective study, we showed that administering Clostridium butyricum MIYAIRI 588 (CBM588) as a live biotherapeutic agent is associated with maintaining intestinal microbiota in the early post-HSCT period. Alpha diversity, which reflects species richness, declined considerably in patients who did not receive CBM588, whereas it remained consistent in those who received CBM588. In addition, ß-diversity analysis revealed that CBM588 did not alter the gut microbiota structure at 7-21 days post-HSCT. Patients who developed GVHD showed structural changes in their microbiota from the pre-transplant period, which was noticeable on day 14 before developing GVHD. Enterococcus was significantly prevalent in patients with GVHD after HSCT, and the population of Bacteroides was maintained from the pre-HSCT period through to the post-HSCT period. Patients who received CBM588 exhibited a contrasting trend, with lower relative abundances of both genera Enterococcus and Bacteroides. These results suggest that preoperative treatment with CBM588 could potentially be beneficial in maintaining intestinal microbiota balance.

Efficacy of elotuzumab for multiple myeloma deteriorates after daratumumab: a multicenter retrospective study.

Elotuzumab-based regimens are sometimes selected for multiple myeloma treatment after daratumumab-based regimens. However, there has been insufficient discussion on the efficacy of elotuzumab after daratumumab. We used Kansai Myeloma Forum registration data in a multicenter retrospective evaluation of the efficacy of elotuzumab after daratumumab. Overall survival (OS) rate and time to next treatment (TTNT) were significantly worse in the cohort given elotuzumab after daratumumab (Dara cohort, n = 47) than in the cohort with no history of daratumumab administration before elotuzumab (No-Dara cohort, n = 80, OS: P = 0.03; TTNT: P = 0.02; best response: P < 0.01). In the Dara cohort, OS and TTNT rates were worse with sequential elotuzumab use after daratumumab than with non-sequential (OS: P = 0.02; TTNT: P = 0.03). In patients given elotuzumab < 180 days after daratumumab, OS (P = 0.08) and best response (P = 0.21) tended to be worse, and TTNT was significantly worse (P = 0.01), than in those given elotuzumab after ≥ 180 days. These findings were confirmed by subgroup analyses and multivariate analyses. Monoclonal-antibody-free treatment might be preferable after daratumumab-based regimens. If possible, elotuzumab-based regimens should be considered only ≥ 180 days after daratumumab use.

[Sequential therapy with inotuzumab ozogamicin followed by CAR T-cell therapy for Philadelphia chromosome-negative acute lymphoblastic leukemia].

A 25-year-old woman with a history of B-cell acute lymphoblastic leukemia over ten years ago was referred to our hospital with a chief complaint of leukoblastosis. She was participating in a JPLSG (Japanese Pediatric Leukemia/Lymphoma Study Group) clinical study at that time. We diagnosed ALL relapse by multi-color flow cytometric analysis of bone marrow samples at admission, with reference to previous JPLSG data. Because her leukemic cells were resistant to conventional cytotoxic agents, she proceeded to lymphocyte apheresis for chimeric antigen receptor T-cell (CAR-T, Tisagenlecleucel [Tisa-cel]). She received two cycles of inotuzumab ozogamicin as a bridging therapy to Tisa-cel, resulting in a hematological complete remission (minimal residual disease measured by polymerase chain reaction [PCR-MRD] was positive at 1.0×10-4). She was finally administered Tisa-cel and achieved MRD negativity. She is currently in complete remission with careful MRD monitoring. This strategy of sequential bi-targeted therapy combining antibody conjugates and CAR-T cells provides tumor control in deeper remission and minimal damage to organ function through reduced use of cytotoxic anti-tumor agents. Therefore, we believe that this therapeutic strategy is an effective and rational treatment for adolescent and young adult ALL patients.

A Nationwide Retrospective Analysis of Allogeneic Hematopoietic Stem Cell Transplantation for Adult Hemophagocytic Lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening disorder characterized by systemic hyperinflammation. Although allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only potentially curative treatment for primary and relapsed/refractory HLH, the optimal strategy has not been established. We retrospectively analyzed 56 adult patients (≥18 years) with primary and secondary HLH (mainly consisting of Epstein-Barr virus-associated HLH) who underwent allo-HSCT using the registry database of the Japanese Society for Transplantation and Cellular Therapy, including 26 patients who underwent cord blood transplantation (CBT). One-fourth of patients received myeloablative conditioning (MAC), mainly consisting of total body irradiation-based regimens. The 3-year overall survival (OS) was 40.6%, while the 3-year cumulative incidences of relapse and non-relapse mortality (NRM) were 19.8% and 39.6%, respectively. In univariable analysis, age at allo-HSCT (the 3-year OS: 27.5% for ≥ 25 years old vs 58.0% for < 25 years old, P = .025), conditioning intensity (7.1% for MAC vs 51.8% for reduced-intensity conditioning (RIC), P = .002), and donor source (26.0% for CBT vs 52.9% for bone marrow or peripheral blood stem cell transplantation (BMT/PBSCT), P = .030) were associated with significantly inferior OS. In multivariable analysis, older age at allo-HSCT (≥ 25 years old) (Hazard ratio [HR], 2.37; 95% CI, 1.01 to 5.58; P = .048), MAC (HR, 2.45; 95% CI, 1.09 to 5.53; P = .031), and CBT (HR, 2.21; 95% CI, 1.04 to 4.71; P = .040) were independently associated with worse OS. In addition, only conditioning intensity predicted higher NRM (the 3-year NRM: 78.6% for MAC vs 26.6% for RIC), while no factors were associated with the relapse rate. This study includes the largest number of adult HLH patients undergoing CBT. Although the use of CBT is acceptable, BMT/PBSCT are more favorable strategies in allo-HSCT in adult HLH. Regarding conditioning intensity, RIC regimens are more beneficial in this setting.

Differentiating Between Epstein-Barr Virus-positive Lymphoid Neoplasm Relapse and Post-transplant Lymphoproliferative Disorder After Sex-mismatched Hematopoietic Stem Cell Transplantation.

After allogeneic hematopoietic stem cell transplantation (HSCT), accurate differentiation between donor-derived post-transplant lymphoproliferative disorder (PTLD) and relapse of recipient-derived lymphoproliferative disorder (LPD) is crucial for determining treatment. Conventional diagnostic approaches for PTLD include histopathological examination, flow cytometry, and chimerism analysis of bulk tumor tissue. However, these methods are inconclusive in cases in which the primary disease is an Epstein-Barr virus (EBV)-positive LPD and is of the same lineage as that of the post-HSCT LPD tumor cells. Particularly, in cases where the number of tumor cells in the tissue is low, it is difficult to determine the origin of tumor cells. In this study, we developed a new method to simultaneously detect signals using sex chromosome fluorescence in situ hybridization, immunofluorescence staining, and EBV-encoded small RNA in situ hybridization on a single section of formalin-fixed paraffin-embedded histopathological specimen. The utility of the method was validated using specimens from 6 cases of EBV-positive LPD after sex-mismatched HSCT that were previously difficult to diagnose, including Hodgkin lymphoma-like PTLD that developed after HSCT for Hodgkin lymphoma and recurrence of chronic active EBV infection. This method successfully preserved the histologic structure after staining and allowed accurate determination of tumor cell origin and lineage at the single-cell level, providing a definitive diagnosis in all cases. This method provides a powerful tool for the diagnosis of LPDs after sex-mismatched HSCT.

Posttransplant cyclophosphamide in unrelated and related peripheral blood stem cell transplantation from HLA-matched and 1 allele mismatched donor.

Posttransplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis has been increasingly used in HLA-haploidentical transplantation and recent studies also demonstrated the efficacy of PTCy in HLA-matched transplantation. We conducted a prospective multicenter phase II study to evaluate the safety and efficacy of PTCy with tacrolimus and mycophenolate mofetil in 43 patients who underwent HLA-matched (n = 21), 1 allele mismatched (n = 20), or 2 allele mismatched (n = 2) peripheral blood stem cell transplantation (PBSCT) following myeloablative (n = 28) or reduced-intensity (n = 15) conditioning. The incidence of grade III-IV acute GVHD at 100 days was 2.3%. The incidences of grades II-IV acute GVHD, all grade chronic GVHD, and moderate to severe chronic GVHD at 2 years were 16.3%, 14.0%, and 4.7%, respectively. Overall survival, disease-free survival, and non-relapse mortality at 2 years were 75.3%, 74.0%, and 7.0%, respectively. GVHD-free, relapse-free survival at 2 years was 67.0%. The rate of off-immunosuppressants in patients who survived without relapse at 2 years was 85.4%. These results indicate that PTCy is a valid option for GVHD prophylaxis in both HLA-matched and HLA 1-2 allele mismatched PBSCT.

Impact of stem cell selection between bone marrow and peripheral blood stem cells for unrelated hematopoietic stem cell transplantation for hematologic malignancies: on behalf of the Donor/Source Working Group of the Japanese Society for Transplantation and Cellular Therapy.

BACKGROUND AIMS: This study aimed to comprehensively assess the impact of stem cell selection between bone marrow (BM) and peripheral blood (PB) in unrelated hematopoietic stem cell transplantation (HSCT) for hematological malignancies. Our objective was to identify specific factors associated with better transplant outcomes. METHODS: A retrospective analysis was conducted using data from the Japanese HSCT registry. Inclusion criteria were patients aged 0-70 years who underwent their first unrelated HSCT with BM or PB, with an 8/8 or 7/8 allele HLA match for hematological malignancies between 2010 and 2020. RESULTS: Among 10 295 patients, no significant difference was observed in overall survival, relapse, graft-versus-host disease (GVHD)-free, relapse-free survival (GRFS) or non-relapse mortality between the groups. Patients who received PB showed no clear difference in acute GVHD but had a greater rate of chronic GVHD, resulting in poor chronic GVHD-free, relapse-free survival (CRFS). Subgroup analyses highlighted the importance of patient-specific factors in source selection. Patients with non-Hodgkin lymphoma and a greater hematopoietic cell transplantation-comorbidity index showed better CRFS and GRFS when BM was the preferred source. Similar trends were observed among patients with standard-risk disease for CRFS. However, no such trends were evident among patients aged 0-24 years, indicating that both sources are viable choices for young patients. CONCLUSIONS: This real-world retrospective analysis showed similar basic outcomes for BM and PB in an unrelated setting. The results support that BM may still be preferred over PB, especially when the long-term quality of life is a major concern. A consideration of individual factors can further optimize transplant success. Further research is warranted to explore the long-term implications of stem cell source selection.

Impact of cytogenetic abnormalities in symptomatic multiple myeloma; a Japanese real-world analysis from Kansai Myeloma Forum.

To evaluate the specific prognostic value of CAs, we conducted an analysis of 923 symptomatic multiple myeloma patients. Among this cohort, 480 patients had complete data set of high-risk CAs by interphase fluorescent in situ hybridization at diagnosis. In the high-risk group analysis, the median OS of patients without CAs (n = 338, 72 %) was 6.5 years, patients with del(17p) (n = 42, 9 %) was 4.4 years, patients with t(4;14) or t(14;16) (n = 72, 15 %) was 4.4 years, and patients with double-positive CAs(del(17p) and t(4;14) or t(14;16)) (n = 18, 4 %) was 2.1 years (p = 0.032). Patients with double-positive CAs had a significantly worse prognosis.

Disseminated non-tuberculous mycobacterial infection caused by Mycobacterium obuense in an immunocompromised patient: a case report.

BACKGROUND: Mycobacterium obuense (M. obuense) is a rapidly growing mycobacterium (RGM) which has been considered nonpathogenic. Here, we report a case of disseminated non-tuberculous mycobacterial (NTM) infection caused by M. obuense in an immunocompromised patient. CASE PRESENTATION: A 16-year-old boy was referred to our hospital due to acute myeloid leukemia. During the treatment of leukemia, the patient exhibited continuous fever, and diffuse miliary nodules with random distribution were found on chest computed tomography. Repeated examinations of bacterial culture tests revealed sputum and urine samples to be smear-positive for acid-fast bacillus, and blood culture from a peripherally inserted central catheter line showed the growth of NTM. The NTM species was identified as M. obuense by mass spectrometry and confirmed by genome sequencing. Combination therapy with amikacin, rifampicin, azithromycin, and moxifloxacin significantly improved the patient's symptoms and radiological findings. CONCLUSION: We report a case of disseminated NTM infection caused by M. obuense for which combination anti-microbial therapy was effective. An immunocompromised host indwelling catheter is at risk of RGM bloodstream infections. Although relatively rare, M. obuense may be considered as a potential pathogen causing infectious diseases, especially in high-risk patients.

[Manufacturing results of tisagenlecleucel for acute lymphoblastic leukemia: a survey by the CAR-T cell therapy taskforce of the Japan Society of Transfusion Medicine and Cell Therapy].

The frequency of the manufacturing failure of chimeric antigen receptor (CAR)-T cell therapy in clinical practice is unknown. To clarify the current state of how likely CAR-T cell production is to succeed or fail for B-cell acute lymphoblastic leukemia (B-ALL), we analyzed cases in which the production of tisagenlecleucel was performed for patients with B-ALL at 15 facilities in Japan from October 2019 to March 2022. Total 81 patients (47 males and 34 females) were analyzed. The median age at apheresis was 13 years (1-25) with a median number of prior treatments of 4 (1-9). The numbers of patients with histories of allogeneic transplantation, inotuzumab ozogamicin, or blinatumomab treatments were 51 (63.0%), 26 (32.1%), and 37 (45.7%), respectively. The median blast percentage and CD3+ cell counts in peripheral blood were 0% (0-91.5), and 611/µl (35-4,210) at apheresis, and the median number of CD3+ cells shipped was 2.2×109 (0.5-8.3). While cases with a history of heavy prior treatment before apheresis were included, no manufacturing failures were observed. Continuing to monitor the status of manufacturing failures is necessary as the number of B-ALL cases treated with CAR-T cell therapy increases.

Risk factors for CAR-T cell manufacturing failure among DLBCL patients: A nationwide survey in Japan.

For successful chimeric antigen receptor T (CAR-T) cell therapy, CAR-T cells must be manufactured without failure caused by suboptimal expansion. In order to determine risk factors for CAR-T cell manufacturing failure, we performed a nationwide cohort study in Japan and analysed patients with diffuse large B-cell lymphoma (DLBCL) who underwent tisagenlecleucel production. We compared clinical factors between 30 cases that failed (7.4%) with those that succeeded (n = 378). Among the failures, the proportion of patients previously treated with bendamustine (43.3% vs. 14.8%; p < 0.001) was significantly higher, and their platelet counts (12.0 vs. 17.0 × 104 /µL; p = 0.01) and CD4/CD8 T-cell ratio (0.30 vs. 0.56; p < 0.01) in peripheral blood at apheresis were significantly lower than in the successful group. Multivariate analysis revealed that repeated bendamustine use with short washout periods prior to apheresis (odds ratio [OR], 5.52; p = 0.013 for ≥6 cycles with washout period of 3-24 months; OR, 57.09; p = 0.005 for ≥3 cycles with washout period of <3 months), low platelet counts (OR, 0.495 per 105 /µL; p = 0.022) or low CD4/CD8 ratios (

Successful Bridging to Allogeneic Hematopoietic Stem Cell Transplantation by Azacitidine and Venetoclax in a Case of Acute Myeloid Leukemia With t(3;3)(q21.3;q26.2) Developed Early After Orthotopic Heart Transplantation.

A 48-year-old male patient developed acute myeloid leukemia (AML) with t(3;3)(q21.3;q26.2) chromosomal mutation 8 months after orthotopic heart transplantation from a human leukocyte antigen-unmatched brain-dead donor for cardiac sarcoidosis. He had sequelae of stroke and chronic renal failure at the time of AML diagnosis. He received 3 cycles of azacitidine and venetoclax induction therapy and achieved complete hematological remission with incomplete count recovery without causing severe complications, including infection. He sequentially underwent allogeneic peripheral blood stem cell transplantation from a HLA-8/8 matched, ABO-blood matched, unrelated female donor and successfully achieved donor cell engraftment. His transplanted heart was viable, and the coronary vessels were not damaged even after allogeneic peripheral blood stem cell transplantation. Although AML relapsed afterward, azacytidine/venetoclax was a tolerable bridging therapy even for early-onset AML after heart transplantation.

Efficacy of elotuzumab for multiple myeloma in reference to lymphocyte counts and kappa/lambda ratio or B2 microglobulin.

Novel therapeutic drugs have dramatically improved the overall survival of patients with multiple myeloma. We sought to identify the characteristics of patients likely to exhibit a durable response to one such drug, elotuzumab, by analyzing a real-world database in Japan. We analyzed 179 patients who underwent 201 elotuzumab treatments. The median time to next treatment (TTNT) with the 95% confidence interval was 6.29 months (5.18-9.20) in this cohort. Univariate analysis showed that patients with any of the following had longer TTNT: no high risk cytogenic abnormalities, more white blood cells, more lymphocytes, non-deviated κ/λ ratio, lower ß2 microglobulin levels (B2MG), fewer prior drug regimens, no prior daratumumab use and better response after elotuzumab treatment. A multivariate analysis showed that TTNT was longer in patients with more lymphocytes (≥ 1400/µL), non-deviated κ/λ ratio (0.1-10), lower B2MG (< 5.5 mg/L) and no prior daratumumab use. We proposed a simple scoring system to predict the durability of the elotuzumab treatment effect by classifying the patients into three categories based on their lymphocyte counts (0 points for ≥ 1400/µL and 1 point for < 1400/µL) and κ/λ ratio (0 points for 0.1-10 and 1 point for < 0.1 or ≥ 10) or B2MG (0 points for < 5.5 mg/L and 1 point for ≥ 5.5 mg/L). The patients with a score of 0 showed significantly longer TTNT (p < 0.001) and better survival (p < 0.001) compared to those with a score of 1 or 2. Prospective cohort studies of elotuzumab treatment may be needed to validate the usefulness of our new scoring system.

[Acquired hemophilia A following BNT162b2 mRNA COVID-19 vaccination].

Acquired hemophilia A (AHA) is a rare disease characteized by bleeding symptoms caused by decreased factor VIII activity due to the appearance of inhibitors to factor VIII triggered by malignancy or collagen disease. An 86-year-old woman developed purpura on her extremities after the first dose of the BNT162b2 mRNA COVID-19 vaccine. This symptom subsided after a few days. After the second dose of the BNT162b2 mRNA COVID-19 vaccine, purpura appeared again, and the patient was referred to our hospital Her APTT was remarkably prolonged to 110 seconds, and a cross-mixing test revealed an inhibitor pattern. Since FVIII activity was <1% and FVIII inhibitor was 51.6 BU, she was diagnosed with AHA. Prednisolone therapy was started, and coagulative complete remission was achieved. Because acquired hemophilia can develop after mRNA COVID-19 vaccination, as in this case, it is critical to monitor the appearance of bleeding symptom.

Clinical utility of genomic profiling of AML using paraffin-embedded bone marrow clots: HM-SCREEN-Japan 01.

Next-generation sequencing of AML has identified specific genetic mutations in AML patients. Hematologic Malignancies (HM)-SCREEN-Japan 01 is a multicenter study to detect actionable mutations using paraffin-embedded bone marrow (BM) clot specimens rather than BM fluid in AML patients for whom standard treatment has not been established. The purpose of this study is to evaluate the presence of potentially therapeutic target gene mutations in patients with newly diagnosed unfit AML and relapsed/refractory AML (R/R-AML) using BM clot specimens. In this study, 188 patients were enrolled and targeted sequencing was undertaken on DNA from 437 genes and RNA from 265 genes. High-quality DNA and RNA were obtained using BM clot specimens, with genetic alterations successfully detected in 177 patients (97.3%), and fusion transcripts in 41 patients (23.2%). The median turnaround time was 13 days. In the detection of fusion genes, not only common fusion products such as RUNX1-RUX1T1 and KMT2A rearrangements, but also NUP98 rearrangements and rare fusion genes were observed. Among 177 patients (72 with unfit AML, 105 with R/R-AML), mutations in KIT and WT1 were independent factors for overall survival (hazard ratio = 12.6 and 8.88, respectively), and patients with high variant allele frequency (≥40%) of TP53 mutations had a poor prognosis. As for the detection of actionable mutations, 38% (n = 69) of patients had useful genetic mutation (FLT3-ITD/TKD, IDH1/2, and DNMT3AR822 ) for treatment selection. Comprehensive genomic profiling using paraffin-embedded BM clot specimens successfully identified leukemic-associated genes that can be used as therapeutic targets.

Different effects of thymoglobulin on acute leukemia with pre-transplant residual blasts in HLA mismatch transplantation.

Anti-thymocyte globulin (ATG) is widely used to reduce acute and chronic graft-versus-host disease (a/cGVHD), one of the leading causes of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). As the removal of alloreactive T cells by ATG may also reduce the graft-versus-leukemia effect, the question of whether ATG use affects relapse incidence and survival outcomes in acute leukemia patients with pre-transplant bone marrow residual blasts (PRB) remains controversial. Here, we evaluated the impact of ATG on transplant outcomes in acute leukemia patients with PRB (n = 994) who underwent HSCT from HLA 1-allele mismatched unrelated donors (MMUD) or HLA 1-antigen mismatched related donors (MMRD). In MMUD with PRB (n = 560), multivariate analysis demonstrated that ATG use significantly decreased grade II-IV aGVHD (hazard ratio [HR], 0.474; P = 0.007) and non-relapse mortality (HR, 0.414; P = 0.029) and marginally improved extensive cGVHD (HR, 0.321; P = 0.054) and GVHD-free/relapse-free survival (HR, 0.750; P = 0.069). We concluded that ATG had different effects on transplant outcomes using MMRD and MMUD, and its use would be beneficial to decrease a/cGVHD without increasing non-relapse mortality and relapse incidence in acute leukemia patients with PRB following HSCT from MMUD.

Prolonged gut microbial alterations in post-transplant survivors of allogeneic haematopoietic stem cell transplantation.

Dysbiosis of the gut microbiota has been reported to increase early complications after allogeneic haematopoietic stem cell transplantation (allo-HSCT). However, it remains unclear whether gut microbial alterations persist during late complications, such as chronic graft-versus-host disease (cGVHD) or secondary cancers. Here, we analysed the gut microbiota of 59 patients who survived for 1-21.7 years (median, 6.4 years) after allo-HSCT. Long-term survivors showed lower gut microbial diversity than the age- and sex-matched healthy controls. This decreased diversity was reflected in the reduced abundance of the butyrate-producing bacteria. Patients with a history of grade 3 acute graft-versus-host disease (aGVHD) exhibited higher Veillonella abundance than patients with a history of grade 1-2 or non-aGVHD cases. The abundance of Faecalibacterium showed no decrease only in limited cGVHD cases. Additionally, the microbial structure in the secondary cancer group was significantly different (p < 0.05) from that in the non-secondary cancer group. This study is the first to show that microbial dysbiosis is present over a 10-year lifetime after discharge following allo-HSCT. Our results suggest that these prolonged gut microbial alterations may be associated with the development and exacerbation of late complications in post-transplant survivors.

Monocyte or white blood cell counts and ß2 microglobulin predict the durable efficacy of daratumumab with lenalidomide.

Background: Daratumumab is one of the most widely used treatments for relapsed/refractory multiple myeloma (MM) patients. However, not all patients achieve a lasting therapeutic response with daratumumab. Objectives: We hypothesized that a durable response to daratumumab could be predicted by the balance between the MM tumor burden and host immune status. Design: We conducted a retrospective study using the real-world data in the Kansai Myeloma Forum (KMF) database. Methods: We retrospectively analyzed 324 relapsed/refractory MM patients who were treated with daratumumab in the KMF database. Results: In this study, 196 patients were treated with daratumumab, lenalidomide, and dexamethasone (DLd) regimen and 128 patients were treated with daratumumab, bortezomib, and dexamethasone (DBd) regimen. The median age at treatment, number of prior treatment regimens and time-to-next-treatment (TTNT) were 68, 4 and 8.02 months, respectively. A multivariate analysis showed that the TTNT under the DLd regimen was longer with either higher monocyte counts (analysis 1), higher white blood cell (WBC) counts (analysis 2), lower ß2 microglobulin (B2MG < 5.5 mg/L) or fewer prior regimens (<4). No parameters were correlated with TTNT under the DBd regimen. Conclusion: We propose a simple scoring model to predict a durable effect of the DLd regimen by classifying patients into three categories based on either monocyte counts (0 points for ⩾200/µl; 1 point for <200/µl) or WBC counts (0 points for ⩾3500/µl; 1 point for <3500/µl) plus B2MG (0 points for <5.5 mg/L; 1 point for ⩾5.5 mg/L). Patients with a score of 0 showed significantly longer TTNT and significantly better survival compared to those with a score of 1 or 2 (both p < 0.001). To confirm this concept, our results will need to be validated in other cohorts.