Patterns of Relapse and Treatment for Relapsed/Refractory AL Amyloidosis: A Systematic Review

Introduction

Amyloidosis is a rare disease and there are currently no FDA approved therapies for AL amyloidosis. Most of the therapeutic and disease data come from expert guidelines, consensus and retrospective review papers. There is a paucity of data specifically for relapsed/refractory AL amyloidosis (RRAL). We conducted this systematic review of clinical trials, retrospective and prospective cohort studies to evaluate patterns of relapse and therapeutic options for RRAL.

Methods

PubMed and Clinicaltrials.gov were searched for clinical trials, retrospective and prospective cohort studies on RRAL. Studies were selected according to PRISMA guidelines. Cross-trial comparison of included studies and meta-analysis could not be performed for a number of reasons but mainly due to a limited number of studies on one particular treatment regimen.

Results

From a total of 511 studies, 11 studies (n= 698 patients) met our inclusion criteria. Five were phase I/II clinical trials, five retrospective cohort studies, and one prospective cohort study. Most studies had less than 50 patients. The largest study, a retrospective cohort by Tandon et al. included 366 patients. Mean age was 61.2.

Three studies reported 2 median prior lines of therapy (n= 22, 28, and 84 patients); two reported 3 median prior lines of therapy (n= 25 and 24) and 6 studies didn't specify this data. Prior treatment options included proteasome inhibitors (PI), most commonly bortezomib (n= 259), followed by melphalan (n=211), high dose melphalan and stem cell transplant (HDM/SCT [n= 207]) and IMiDs most commonly lenalidomide (n=154).

Time to progression (TTP) from first-line treatment was reported in only 4 studies as 1 month, 5 months, 5 months and 34 months respectively. The study reporting a TTP of 34-months had 11 patients who received HDM/SCT as first line treatment. Three studies reported information about their criteria for initiation of subsequent treatment.

Subsequent treatment was mostly a combination regimen with dexamethasone or an alkylating agent. The only agent evaluated as single agent was bortezomib in a phase I/II clinical trial by Reece et al. Therapeutic options for RRAL are PI (non-specific) based therapy (n= 145), lenalidomide (n= 105), bortezomib (n= 99), IMiD (non-specific) based therapy (n=83), melphalan based therapy (n= 33), carfilzomib (n=28), pomalidomide (n=27), ASCT (n= 25), daratumumab (n=25) and bendamustine (n=22).

Efficacy: Hematologic responses were reported to be following: bortezomib + dexamethasone/melphalan (85%, n=17/20), daratumumab + dexamethasone (76%, n= 19/25), HDM/ASCT (73%, n= 8/11), single agent bortezomib (67%, n=23/34), carfilzomib ± dexamethasone (63%, n= 15/24), lenalidomide + dexamethasone (61%, n=51/84), bendamustine + dexamethasone (55%, 11/22) and pomalidomide + dexamethasone (50%, 12/24). Five of eleven studies reported organ responses which ranged from 18% to 23%. The studies which reported organ responses had evaluated the following agents: single agent bortezomib, carfilzomib ± dexamethasone, lenalidomide + dexamethasone, and bendamustine + dexamethasone. Best survival outcomes were seen with bortezomib with median overall survival (OS) 62 months. With bendamustine and dexamethasone (retrospective cohort study n=22) median OS was 31 months. With lenalidomide + dexamethasone (prospective cohort study n=24 ) median OS was 14 months. For the remaining studies, the median OS was either not reported or not reached at the time of presentation of data.

Conclusion

AL amyloidosis patients progressing after front line therapy show good responses with bortezomib (median overall survival of 62 months). Novel combinations using lenalidomide, pomalidomide, carfilzomib, daratumumab, and bendamustine show promising efficacy. Ongoing trials of daratumumab (AMYDARA trial) and ixazomib (TOURAMALINE-AL1) will bring further insight into therapeutic armamentarium for RRAL patients. After relapse, a salvage HDM/ASCT can be considered. Comparisons of regimen efficacy between studies are not practical because of multiple factors which include but are not limited to heterogenous nature of AL patients, small sample sizes, variable prior treatments, exposure to novel agents, observational study versus clinical trial and variable endpoints.

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