Background: Daratumumab and bortezomib, the first-line regimens for AL amyloidosis, typically yield a complete hematologic response rate of nearly 60%. The median time to a hematologic response for the daratumumab based treatment is only 7-9 days. An early achievement of a complete hematologic response (CR) is particularly crucial in amyloidosis.

Methods: We retrospectively evaluated the relationship between dFLC (the difference between free light chain) reduction in C1D7 and complete hematologic response, organ response, and survival in newly diagnosed AL amyloidosis patients receiving daratumumab, bortezomib, and dexamethasone.

Results: The hematologic CR rate within six months for 48 patients was 66.7%. The median time to initial hematologic response among these patients was 7 days (range, 7-31), while the median time to achieve the best hematologic response was 2 months (range, 0.23-9). Using Receiver Operating Characteristic Curve (ROC) curve analysis, we predicted hematologic CR based on a dFLC reduction 7 days post-treatment (67.0% change, optimal sensitivity 87.5%, specificity 81.3%). We introduce the novel concept of “rapid hematologic dFLC response”, which is defined as a reduction in dFLC levels ≥ 67% after 7 days. The CR rate was 90.3% in rapid responders' groups while 23.5%in slow responders' group (P ＜0.01). After a median follow-up of 19 months (range: 0.3-57), cardiac and renal response achieved 72.0%, 62.8% in rapid responders' group while 43.8%, 40% in slow responders' group (P=0.104, P=0.025). The median major organ deterioration event-free survival (MOD-EFS) in rapid responders' group (not reached) was significantly superior than that in slow responders' group (19m, 95% CI: 1.785-23.14m, P=0.048).

Conclusion: Early dFLC reduction 7 days post-treatment indicates a high possibility of complete hematologic response and organ response. We propose a new concept of “the rapid hematologic dFLC response” in AL amyloidosis, based on treatment with daratumumab, bortezomib, and dexamethasone.

Disclosures

No relevant conflicts of interest to declare.

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2024
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