Achievement of a normal FLC ratio (FLCr) following treatment indicates hematologic response and suggests better outcomes in light chain amyloidosis (AL). We examined if elevated involved free light chain (hiFLC) impacts outcomes in patients achieving normal FLCr. We retrospectively analyzed 345 AL patients who were diagnosed within a 10-year period (2006-2015) and had 2 consecutive normal FLCr values after 1st line treatment. Among these, patients with hiFLC at 1st reading of normal FLCr (hiFLC1; n=166; 48.1%) were compared to those who did not (n=179; 51.9%). Patients with AL who have hiFLC1 after initial therapy had higher rates of multi-organ involvement (63.3 vs 46.4%; P=.002) and patients in advanced Mayo stage (42.9 vs 32.2%; P=.04) at diagnosis. The median progression free survival [PFS; 38.2 (95%CI; 26.4, 55.4) vs 67.1 (95%CI; 55.8, 88) months; P=.0002] and overall survival [OS; 94.4 (95%CI; 78, 107.1) vs not reached (NR, 95%CI; 116.1, NR) months; P<.0001] were lower in those who had hiFLC1. A more stringent comparison for patients with 2 consecutive hiFLC (hIFLC2; n=111; 32.2%) versus not (n=2234; 67.8%) showed consistent results [PFS; 27.1 (95%CI; 23, 53.8) vs 63.3 (95%CI; 55.4, 77) months; P<.0001 and OS; 78 (95% CI; 54.6, 98.8) vs NR (95%CI; NR, NR); P<.0001]. This poor prognostic impact of hiFLC on survival was independent of serum creatinine, Mayo stage, negative immunofixation status and inclusion of transplant in initial therapy on multivariate analysis. Hence, persistent elevation of iFLC predicts poor prognosis even among patients achieving normal ratio after initial therapy in AL.
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