**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Marco Basset; Amyloidosis Research and Treatment Center, IRCCS Policlinico San Matteo, University of Pavia, Pavia, Italy

**Main Body of the Abstract**
IgM-AL amyloidosis is a rare distinct entity, characterized by clonal heterogeneity. Although several retrospective identified prognostic factors, some questions remained unanswered, as the prognostic role of dFLC and IgM concentration at diagnosis and after treatment. Patients with IgM-AL amyloidosis evaluated at the at the Heidelberg Amyloidosis Center between May 2003-December 2019 were included in the study. Multivariable analysis was performed to identify prognostic factors for overall survival (OS) and hematologic progression-free survival (hemEFS). One-hundred patients were included in the study. The B-cell clone showed a lymphoid immunophenotype (lymphC) in 64% and plasma cellular (pcC) in 28% cases. Sixteen patients received chemotherapy for the underlying clonal disease before diagnosis of AL amyloidosis. Median OS and hemEFS were 42 and 15 months. On multivariable analysis (Table1), dFLC(log10) was prognostic for OS (HR 2.51, P<0.001) and hemEFS (HR 2.04, P=0.002), while IgM concentration showed just a trend for worse hemEFS (HR 1.02, P=0.056). Severity of heart involvement, assessed by European Mayo stage, was confirmed prognostic for OS (overall P=0.004). After first-line treatment (rituximab-based in 72% of lymphC and 8% of pcC), hematologic response, assessed both by reduction in dFLC and IgM concentration, resulted in better OS. However, patients who achieved an IgM-response but not a dFLC-response had a shorter OS compared to those with a response also according to dFLC (n=16, median 14 months vs. not reached; P=0.009). In IgM-AL amyloidosis, dFLC is confirmed as a relevant prognostic factor, along with European Mayo stage.



**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Marco Basset; _Amyloidosis Research and Treatment Center, IRCCS Policlinico San Matteo, University of Pavia, Pavia, Italy_

**Main Body of the Abstract**
IgM-AL amyloidosis is a rare distinct entity, characterized by clonal heterogeneity. Although several retrospective identified prognostic factors, some questions remained unanswered, as the prognostic role of dFLC and IgM concentration at diagnosis and after treatment. Patients with IgM-AL amyloidosis evaluated at the at the Heidelberg Amyloidosis Center between May 2003-December 2019 were included in the study. Multivariable analysis was performed to identify prognostic factors for overall survival (OS) and hematologic progression-free survival (hemEFS). One-hundred patients were included in the study. The B-cell clone showed a lymphoid immunophenotype (lymphC) in 64% and plasma cellular (pcC) in 28% cases. Sixteen patients received chemotherapy for the underlying clonal disease before diagnosis of AL amyloidosis. Median OS and hemEFS were 42 and 15 months. On multivariable analysis (Table1), dFLC(log10) was prognostic for OS (HR 2.51, P<0.001) and hemEFS (HR 2.04, P=0.002), while IgM concentration showed just a trend for worse hemEFS (HR 1.02, P=0.056). Severity of heart involvement, assessed by European Mayo stage, was confirmed prognostic for OS (overall P=0.004). After first-line treatment (rituximab-based in 72% of lymphC and 8% of pcC), hematologic response, assessed both by reduction in dFLC and IgM concentration, resulted in better OS. However, patients who achieved an IgM-response but not a dFLC-response had a shorter OS compared to those with a response also according to dFLC (n=16, median 14 months vs. not reached; P=0.009). In IgM-AL amyloidosis, dFLC is confirmed as a relevant prognostic factor, along with European Mayo stage.



IgM Immunoglobulin light chain amyloidosis: the quest for prognostic biomarkers in a rare disease with two distinct clonal phenotypes PA130 (#467)

We invite you to attend the XIX International Symposium on Amyloidosis to be held in Rochester, MN.

This symposium is organized as a hybrid meeting (with the focus on in-person) held from Sunday, May 26 through Thursday, May 30, 2024.

Together with the ISA Board and members of Mayo Clinic, a very attractive scientific hybrid program is being planned. The program will cover a variety of types of systemic amyloidosis: ATTR (hereditary and wild-type), AL (light-chain), AA and less frequent forms. There will be key lectures, specific symposia including those company sponsored, oral presentations and poster sessions of accepted abstracts.

COURSE DESCRIPTION
This program will provide a comprehensive review of state-of-the-art education in systemic amyloidosis: basic science, pathophysiology, diagnosis, current and emerging treatments. Scientific presentations will include competitive oral and poster abstracts. The rapid evolution of scientific discovery and expanding treatment options has created tremendous interest in the field and this meeting will fill and important gap in educating scientists and clinicians.