Timing and impact of a deep response in the outcome of patients with systemic light chain (AL) amyloidosis.

A rapid and deep haematologic response is fundamental in order to improve outcomes of patients with AL amyloidosis. We evaluated the impact of timing and depth of haematologic response at early time points (at 1 and 3 months from the start of therapy) in 227 consecutive previously untreated AL patients, who received bortezomib-based primary therapy. After 1 month of therapy, 30.5% had ≥VGPR, 28% PR and 36% no response (NR), with 11% having iFLC <20 mg/L and 15% dFLC <10 mg/L. Deep haematologic response at 1 month (either ≥VGPR or iFLC <20 mg/L or dFLC <10 mg/L), was associated with a high organ response rate. The survival of patients with ≥VGPR was significantly better than those with PR and NR at 1-month landmark (p < .001) but this benefit was mainly driven by those with iFLC <20 mg/L. The depth of haematologic response at 1 month was significant across all Mayo stages. At 3 months, 46% of the patients had not significantly improved the depth of their response but even patients that improved their response from an iFLC ≥20 mg/L at 1 month to iFLC <20 mg/L at 3 months still had inferior outcome to those with an early deep response. Thus, in patients with AL amyloidosis, a very rapid and deep response is crucial, especially for those at high risk, targeting very low FLC levels within the first month of therapy.