Clonal Hematopoiesis after Autologous Stem Cell Transplantation Does Not Confer Adverse Prognosis in Patients with AML

Clonal hematopoiesis of indeterminate potential is rare in pediatric patients undergoing autologous stem cell transplantation

Clonal hematopoiesis of indeterminate potential (CHIP) describes recurrent somatic gene mutations in the blood of healthy individuals, associated with higher risk for hematological malignancies and higher all-cause mortality by cardiovascular disease. CHIP increases with age and is more common in adult patients after chemotherapy or radiation for cancer. Furthermore, in some adult patients undergoing autologous stem cell transplantation (ASCT) or thereafter, CHIP has been identified. In children and adolescents, it remains unclear how cellular stressors such as cytotoxic therapy influence the incidence and expansion of CHIP. We conducted a retrospective study on 33 pediatric patients mostly with solid tumors undergoing ASCT for presence of CHIP. We analyzed CD34+ selected peripheral blood stem cell grafts after several cycles of chemotherapy, prior to cell infusion, by next-generation sequencing including 18 "CHIP-genes". Apart from a somatic variant in TP53 in one patient no other variants indicative of CHIP were identified. As a CHIP-unrelated finding, germline variants in CHEK2 and in ATM were identified in two and four patients, respectively. In conclusion, we could not detect "typical" CHIP variants in our cohort of pediatric cancer patients undergoing ASCT. However, more studies with larger patient numbers are necessary to assess if chemotherapy in the pediatric setting contributes to an increased CHIP incidence and at what time point.

The crossroads of cancer therapies and clonal hematopoiesis

The intricate interplay between Clonal Hematopoiesis (CH) and the repercussions of cancer therapies has garnered significant research focus in recent years. Previously perceived as an age-related phenomenon, CH is now closely linked to inflammation ("Inflammaging") and cancer, impacting leukemogenesis, cancer progression, and treatment responses. This review explores the complex interplay between CH and diverse cancer therapies, including chemotherapy, targeted treatments, radiation, stem cell transplants, CAR-T cell therapy, and immunotherapy, like immune checkpoint inhibitors. Notably, knowledge about post-chemotherapy CH mutation/acquisition has evolved from a de novo incident to more of a clonal selection process. Chemotherapy and radiation exposure, whether therapeutic or environmental, increases CH risk, particularly in genes like TP53 and PPM1D. Environmental toxins, especially in high-risk environments like post-disaster sites or space exploration, are associated with CH. CH affects clinical outcomes in stem cell transplant scenarios, including engraftment, survival, and t-MN development. The presence of CH also alters CAR-T cell therapy responses and impacts the efficacy and toxicity of immunotherapies. Furthermore, specific mutations like DNMT3A and TET2 thrive under inflammatory stress, influencing therapy outcomes and justifying the ongoing tailored interventions in clinical trials. This review underscores the critical need to integrate CH analysis into personalized medicine, enhancing risk assessments and refining treatment strategies. As we progress, multidisciplinary collaboration and comprehensive studies are imperative. Understanding CH's impact, especially concerning genotoxic stressors, will inform screening, surveillance, and early detection strategies, decreasing the risk of therapy-related myeloid neoplasms and revolutionizing cancer treatment paradigms.

The latest edition of WHO and ELN guidance and a new risk model for Chinese acute myeloid leukemia patients

Objective

Diagnosis classification and risk stratification are crucial in the prognosis prediction and treatment selection of acute myeloid leukemia (AML). Here, we used a database of 536 AML patients to compare the 4th and 5th WHO classifications and the 2017 and 2022 versions of ELN guidance.

Methods

AML patients were classified according to the 4th and 5th WHO classifications, as well as the 2017 and 2022 versions of the European LeukemiaNet (ELN) guidance. Kaplan-Meier curves with log-rank tests were used for survival analysis.

Results

The biggest change was that 25 (5.2%), 8 (1.6%), and 1 (0.2%) patients in the AML, not otherwise specified (NOS) group according to the 4th WHO classification, were re-classified into the AML-MR (myelodysplasia-related), KMT2A rearrangement, and NUP98 rearrangement subgroups based on the 5th WHO classification. Referring to the ELN guidance, 16 patients in the favorable group, six patients in the adverse group, and 13 patients in the intermediate group based on the 2017 ELN guidance were re-classified to the intermediate and adverse groups based on the 2022 ELN guidance. Regrettably, the Kaplan-Meier curves showed that the survival of intermediate and adverse groups could not be distinguished well according to either the 2017 or 2022 ELN guidance. To this end, we constructed a risk model for Chinese AML patients, in which the clinical information (age and gender), gene mutations (NPM1, RUNX1, SH2B3, and TP53), and fusions (CBFB::MYH11 and RUNX1::RUNX1T1) were included, and our model could help divide the patients into favorable, intermediate, and adverse groups.

Conclusion

These results affirmed the clinical value of both WHO and ELN, but a more suitable prognosis model should be established in Chinese cohorts, such as the models we proposed.

BeEAM Conditioning including High-Dose Bendamustine before Autologous Stem Cell Transplantation Is Safe and Effective in Patients with Waldenstrom's Macroglobulinemia

High-dose chemotherapy (HDCT) with autologous stem cell transplantation (ASCT) is an option to consolidate remission in Waldenstrom's macroglobulinemia (WM), particularly in selected younger patients with chemosensitive disease. BEAM, consisting of BCNU, etoposide, cytarabine, and melphalan, is often used as a conditioning regimen. However, problems with BCNU, including pneumotoxicity, tolerance, and availability, necessitate the search for alternatives. In this pilot study, we investigated high-dose chemotherapy with BeEAM, in which BCNU is replaced with high-dose bendamustine as an alternative conditioning regimen in six subsequent patients with WM. Bendamustine treatment was well tolerated without unexpected toxicities. The overall response rate was 6/6 patients (2 very good partial responses (VGPR) and 4 PR). After a median follow-up of 72 months, two (33%) patients relapsed. Median progression-free and overall survivals were not reached, and no severe late-onset toxicities were observed so far. In this pilot study, BeEAM conditioning before ASCT seems feasible, safe, and effective in patients with WM.

Clonal Hematopoiesis: Role in Hematologic and Non-Hematologic Malignancies

Hematopoietic stem cells (HSCs) ensure the coordinated and balanced production of all hematopoietic cell types throughout life. Aging is associated with a gradual decline of the self-renewal and regenerative potential of HSCs and with the development of clonal hematopoiesis. Clonal hematopoiesis of indeterminate potential (CHIP) defines the clonal expansion of genetically variant hematopoietic cells bearing one or more gene mutations and/or structural variants (such as copy number alterations). CHIP increases exponentially with age and is associated with cancers, including hematologic neoplasia, cardiovascular and other diseases. The presence of CHIP consistently increases the risk of hematologic malignancy, particularly in individuals who have CHIP in association with peripheral blood cytopenia.

Clonal hematopoiesis: Mutation-specific adaptation to environmental change

Clonal hematopoiesis of indeterminate potential (CHIP) describes a widespread expansion of genetically variant hematopoietic cells that increases exponentially with age and is associated with increased risks of cancers, cardiovascular disease, and other maladies. Here, we discuss how environmental contexts associated with CHIP, such as old age, infections, chemotherapy, or cigarette smoking, alter tissue microenvironments to facilitate the selection and expansion of specific CHIP mutant clones. Further, we consider major remaining gaps in knowledge, including intrinsic effects, clone size thresholds, and factors affecting clonal competition, that will determine future application of this field in transplant and preventive medicine.