Zanwar, Saurabh S

Abstract This retrospective analysis examined 15 years of autologous stem cell transplantation (ASCT) for light chain (AL) amyloidosis at the Mayo Clinic (2010-2024). We aimed to assess ASCT utilization trends, factors influencing practice changes, and current indications amid newer therapies. Four hundred and forty-one ASCTs were divided into cohort 1 (2010-2019) and cohort 2 (2020-2024), revealing a significant ASCT reduction in cohort 2 (385 vs 56, average 71% annual decrease). Cohort 2 patients were older, more likely to have relapsed/refractory disease, and had higher baseline bone marrow plasma cell burden compared to cohort 1. Pre-ASCT induction was more frequent in cohort 2 (89.3% vs 56.4%), with daratumumab (Dara)–cyclophosphamide-bortezomib-dexamethasone (CyBorD) replacing CyBorD as the predominant induction regimen. Lymphoma-based regimens were also more common in cohort 2 (15.1% vs 5.3%, P = .02). Day-100 satisfactory hematological response improved in cohort 2 (91.1% vs 72.7%, P = .001), although hematological complete response rates did not significantly differ (50.9% vs 38.8%, P = .09). In summary, there is a decrease in the utilization of ASCT in AL amyloidosis. This procedure is primarily reserved for patients with suboptimal responses, relapsed/refractory disease, lymphoplasmacytic clones (predominantly immunoglobulin M amyloidosis), or high bone marrow plasma cell burden (myeloma phenotype). This study underscores a significant shift in ASCT practice, driven by novel therapies, emphasizing more personalized management in AL amyloidosis.

Extramedullary multiple myeloma (EMM), defined in this review as soft tissue plasmacytomas resulting from hematogenous spread, is characterized by the ability of MM cells to proliferate outside of the bone marrow microenvironment. It is aggressive, often associated with high-risk cytogenetics and early relapse, and independently portends significantly shorter progression-free and overall survival, even in the era of highly effective immunotherapies. The molecular and microenvironmental factors underlying extramedullary MM dissemination continue to be studied to inform the development of better treatments. In this review, we discuss our current understanding of the biology of EMM, focusing on its distinct molecular and microenvironmental characteristics vis-à-vis MM. We also review the current treatment strategies, acknowledging the paucity of large, randomized studies specific to this population.

ABSTRACT As the treatment paradigm for Waldenström macroglobulinemia (WM) continues to evolve, the debate surrounding the prioritization of depth of response versus disease control as therapeutic goals gains significant relevance. However, the impact of depth of response from fixed‐duration therapy on overall survival (OS) was unclear. This multicenter study evaluated the prognostic impact of depth of response using a landmark survival analysis. A total of 440 patients with WM treated with frontline fixed‐duration regimens were included. Attaining a major response (MaR) was associated with superior outcomes, including significantly longer OS. The estimated 5‐year PFS rates for patients with MaR at 6 months versus not were 50% versus 32%, respectively, p < 0.001, and the estimated 5‐year OS rates for patients with MaR at 6 months versus not were 89% versus 70%, respectively, p < 0.001. In a multivariable analysis, MaR at 6 months was independently associated with superior PFS (HR 0.66, p = 0.007) and OS (HR 0.28, p < 0.001). Similar results were seen when considering deeper responses (CR + VGPR vs. PR). Depth of response at 6 months is an important prognostic marker in WM and an independent predictor of PFS and OS. These results support its utilization as a suitable endpoint in clinical studies in WM.

PURPOSE BRAF and MEK inhibitors are standard treatments in histiocytic disorders, such as Erdheim-Chester disease (ECD). Some patients lack MAPK-pathway alterations, making these treatments less effective. METHODS We describe three patients with histiocytic disorders who have novel non-MAPK pathway alterations. These alterations were studied through genomic and in silico analyses when applicable, then treated with off-label medications rationally selected on the basis of genomic alterations. RESULTS Patient 1 had rapidly progressive ECD involving the CNS. A CSF1R in-frame deletion (p.S560_P566del) was identified, and in silico modeling predicted a gain-of-function mutation. This alteration was targeted with pexidartinib, which led to a clinical complete response (CR) within 2 months, and a partial response (PR) on imaging after 3 months. After 15 months, the disease became resistant to pexidartinib and transformed to histiocytic sarcoma. Patient 2 has skin-only involvement of a xanthogranuloma disorder. A KIF5B-FGFR1 fusion was identified on RNA sequencing and targeted with pemigatinib. At 24 months of follow-up, she remains in a clinical PR. Patient 3 has ECD involving the bone marrow, gastrointestinal tract, and subcutaneous tissues. A MEF2C-FLT3 fusion was identified and targeted with sorafenib. He achieved a clinical CR and radiographic PR within 3 months, which has continued for 30 months. CONCLUSION We report three patients with histiocytic disorders harboring novel alterations who had sustained responses to off-label kinase inhibitors specific to their histiocytic disorder. Pathogenic variants outside of the MAPK pathway, including variants of unknown significant, may be targeted with readily available small molecules.