Abstract Body (Do not enter title and authors here): Introduction
AL cardiac amyloidosis (AL-CA) is associated with poor prognosis, largely driven by cardiac involvement. The revised Mayo staging system utilizes cardiac biomarkers to risk-stratify and predict outcomes for these patients. However, its long-term predictive value remains uncertain, particularly in the era of novel therapies. This study evaluated the prognostic impact of the revised Mayo staging system, especially on five- and ten-year survival outcomes in AL-CA patients.

Methods
We conducted a retrospective cohort study of patients diagnosed with AL-CA at our quaternary center between January 2012 and December 2022. Non-AL amyloidosis patients and those lacking complete data were excluded. Overall survival (OS) was defined from the date of diagnosis until death. Cox regression evaluated associations between Mayo staging and survival.

Results
Of 411 patients included, 63.7% were male, 78.6% white, with a median age at AL-CA diagnosis of 68 years (IQR: 31–92). Mayo staging distribution was: stage I (3.6%), stage II (12%), stage III (27.7%), and stage IV (55.5%). During a median follow-up of 25.7 months (IQR: 4.7,56.2), 60.8% (n=250) of patients died. Survival differed significantly by Mayo stage, with a median OS of 80.2 months in stage II, 47.2 months in stage III, and 12.8 months in stage IV (log-rank p < 0.0001) (Figure 1). On multivariable Cox regression, increasing age was independently associated with worse survival (HR = 1.02, 95% CI: 1.01–1.04, p<0.001). Compared to Mayo stage I/II, stage III (HR = 2.02, p=0.005) and stage IV (HR = 2.98, p<0.001) were associated with significantly higher mortality. NYHA class IV was also independently associated with increased risk of death (HR = 1.77, p=0.035) (Figure 2) (Table 1)
Long-term follow-up indicated that the 5-year OS was 53.6% (stage I), 73.3% (stage II), 45.5% (stage III), and 32.8% (stage IV). Ten-year OS was 53.6% (stage I), 47.1% (stage II), 23.9% (stage III), and 22.1% (stage IV). Notably, 67% of stage IV survivors at five years remained alive at ten years, comparable to stage II (64%).

Conclusion
The revised Mayo staging remains prognostic for AL-CA, demonstrating significant stage-based survival differences. Despite improved outcomes with contemporary treatments, advanced-stage disease remains associated with poorer survival. Importantly, patients in higher-risk stages who reach the five-year mark maintain a substantial likelihood of long-term survival similar to those with less severe stages