Cardiac complete response in AL amyloidosis: Phenotypic characteristics, functional recovery, and survival outcomes of 63 patients

Abstract Cardiac involvement in AL amyloidosis significantly impacts both short and long-term survival. Achieving cardiac complete response (CarCR) is linked to excellent survival, comparable to that of the general population. We undertook this study to characterize patients with AL amyloidosis who achieved CarCR. Methods: A single-center retrospective study of patients diagnosed with cardiac AL amyloidosis between 2004 and 2023 and achieved a documented CarCR for at least 12 months. Patients were included if they had evidence of cardiac involvement confirmed by cardiac imaging (transthoracic echocardiogram or cardiac magnetic resonance) and Congo red–positive tissue (non-cardiac or heart biopsy), and were evaluable for cardiac response based on baseline NT-proBNP > 650 pg/mL or BNP > 150 pg/mL. CarCR was defined as a reduction in NT-proBNP to less than 350 pg/mL (or BNP less than 80 pg/mL). Heart transplant patients were excluded. Results: Sixty-three patients were included, representing 4.6% of the cardiac evaluable population in the study period. This proportion increased in the second period compared to the first period (7.5% vs 3.2%, P<0.001). The median age at diagnosis of 57 years (ranging from 29 to 79); 63% were male. Lambda light chain disease was evident in 63% of patients. The median difference between the involved and uninvolved light chain (dFLC) at baseline was 429 mg/L (interquartile range [IQR] 143-708). While all patients had cardiac involvement, 63% also presented with extra-cardiac involvement [kidneys (52%), liver (16%), autonomic nerves (14%), luminal gastrointestinal tract (11%), and peripheral nerves (10%)]. The median baseline NT-proBNP for the entire cohort was 1977 pg/mL (IQR 1393-3026). The median troponin T (n=43) was 0.02 ng/mL (IQR <0.01-0.05) and the median high-sensitivity troponin T (n=19) was 49 ng/L (IQR 38-79 ng/L). Cardiac stage distribution, according to the European modification of the Mayo 2004 staging model, was as follows: 59% stage II, 39% stage IIIa, and 2% stage IIIb. At baseline, echocardiogram features included a median left ventricular (LV) ejection fraction of 63%, a median intraventricular septum thickness of 14 mm, and a median average LV longitudinal strain of -12%. The most common first-line therapies were autologous stem cell transplantation (ASCT; with or without induction, 54%), bortezomib-containing therapy (22%), and daratumumab-containing therapy (13%). Hematological complete response rates at 3-month, 6-month, and best response prior to CarCR were 32%, 49% and 76%, respectively. At CarCR, the median NT-proBNP was 265 pg/mL (IQR 220-307) with a median time from treatment onset to CarCR achievement of 20.6 months. At CarCR, 33% of patients were on loop diuretics. The CarCR rate at 6, 12, 24, 36, 48 and 60 months from treatment onset was 10%, 39%, 81%, 90%, 95% and 96%, respectively. Temporary increase of NT-proBNP above 350 pg/mL with return to CarCR was documented in 46% of patients. Echocardiogram parameters also improved significantly at the time of CarCR, with average left ventricular longitudinal strain showing the greatest median improvement in relation to baseline (from -12% to -17%, p<0.001). However, echocardiographic parameters did not fully normalize in all patients. Cardiac progression was seen in 14% of patients, at a median of 7.6 years from the initial time of CarCR. In addition, subsequent clone-directed therapy was given in 44% of patients at a median of 4.6 years from the initial treatment. With a median follow-up of 9.5 years, eight patients (13%) died, 4 due to causes unrelated to AL. We compared the survival of patients who achieved CarCR to the general U.S. population, matching for age, sex, and the year treatment. The observed survival of CarCR patients was similar to that of the general population (p=0.35). Conclusion: Patients with persistent CarCR >12 months in AL amyloidosis are uncommon and demonstrate excellent outcomes. The achievement of hematological CR was required in 3 out of 4 patients reaching a CarCR. Echocardiographic changes of amyloid infiltration may still persist in this highly favorable cohort, indicating that “complete” response refers primarily to functional and prognostic improvement, not necessarily a full restoration to pre-disease cardiac morphology and function. Achieving CarCR is associated with a low risk of cardiac progression, but the need for subsequent clone-directed therapy remains elevated.