Risk Factors for Early Sudden Cardiac Death in Patients with Systemic Light-Chain Amyloidosis on Treatment

Introduction: Despite advances in therapy for patients with light-chain (AL) amyloidosis, mortality remains high in the first 6 months after diagnosis in those on treatment (Blood 2017;129:2111). The early deaths are usually sudden cardiac deaths (SCD); a prior study showed that troponin I level and lack of response to therapy influenced survival (Br J Haematol 2008;143:369). In January 2021 at the approval of daratumumab with cyclophosphamide, bortezomib and dexamethasone for AL (Dara/CyBorD), the FDA label warned that patients with higher cardiac staging may be at risk for fatal cardiac events. We sought to analyze risk factors for SCD in patients on treatment, defining SCD as a sudden unexpected death caused by loss of cardiovascular function (Arrhythm Electrophysiol Rev 2016;5:177).

Methods: From a database of 398 patients with AL amyloidosis collected from 2005-2019, we identified patients who suffered out-patient SCD on treatment within 180 days of diagnosis. We recorded baseline age, gender, systolic BP, presence of syncope, LVEF, FLC, cardiac biomarkers, NYHA class, cycles of treatment with bortezomib, and data on SCD. For comparison we identified an age and gender matched group who achieved complete or very good partial responses (CR or VGPR) based on standard criteria and recorded that group's data (J Clin Oncol 2012;30:4541). We compared these datasets by two-tailed Mann-Whitney and where appropriate by contingency table analysis. We computed the medians of the involved FLC, BNP and troponin for all the cases to determine the frequency with which patients in either group had baseline values above or below those medians.

Results: Comparative results are shown in Table 1. We identified 13 SCD and 74 age and gender matched CR/VGPR patients. Compared with the CR/VGPR group, both hypotension and exertional syncope were significantly more common in the SCD group, indicating the presence of autonomic dysfunction. NYHA class 3 or 4 status was also more common in the SCD group (40% and 13% vs 26% and 13% in the CR/VGPR group). In addition, more SCD patients were Mayo cardiac stage III (80% vs 46% in the CR/VGPR group) (Blood 2004;104:1881; J Clin Oncol 2004;22:3751). The SCD patients had significantly lower LVEF and higher iFLC and were significantly more likely to have iFLC values above the median. Similarly they had significantly higher BNP and troponin-I levels and were more likely to have values above the medians. The causes of death were unclear in 9 cases but were described by witnesses as due to syncopal events associated with micturition, climbing stairs, or light exertion. In 4 cases seen in emergency rooms, PEA was documented in 3 and septic shock in 1.

The SCD patients had a median of 1 cycle of subcutaneous bortezomib-based therapy (CyBorD) (range, 1-5). Three patients received daratumumab subcutaneously with CyBorD. The median starting dose of bortezomib was 1.3mg/m2 (0.7-1.5) usually on a weekly schedule; 2 patients initiated therapy at 1.5mg/m2 weekly, one of whom had had progression of disease (POD) after 2 cycles of oral melphalan and dexamethasone and then had further progression despite completing 3 cycles of CyBorD (POD=1). Eight patients were inevaluable for hematologic response (NR=8), 2 achieved PR after 2 and 4 cycles of CyBorD (PR=2), and of the 3 who got Dara/CyBorD, 1 was inevaluable, 1 achieved VGPR after C1 and 1 CR in C2 (CR/VGPR=2), before having SCD.

Conclusion: These findings indicate the contribution that the presence of autonomic dysfunction makes in this population of AL patients with advanced cardiac disease and high levels of iFLC, key variables in the revised Mayo staging system (J Clin Oncol 2012;30:989). The potential pre-morbid significance of exertional syncope has been identified previously (Am J Cardiol 1997;80:1242). In conclusion, this case series suggests that compared with AL amyloid patients who achieve CR or VGPR with treatment, patients who suffer early SCD on treatment have symptoms indicative of autonomic dysfunction and may benefit from in-patient initiation of treatment and from obtaining insurance approval for Dara/CyBorD but starting therapy with weekly subcutaneous daratumumab and dexamethasone, adding cyclophosphamide and bortezomib at a later timepoint based on hematologic response. Moreover, weekly assessment of FLC response is reasonable in these patients in order to guide therapy and adjust supportive care.

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