Relapse Rate and Long-Term Survival of AL Amyloidosis Patients Treated with High-Dose Melphalan and Autologous Stem Cell Transplantation (HDM/SCT).

AL amyloidosis is a plasma cell dyscrasia in which clonal immunoglobulin light chains misfold and are deposited in tissues, leading to organ failure in untreated patients, with median survival of only ~1 year. Oral melphalan and prednisone is minimally effective for the disease, with an increase in median survival to ~1.5 years, and a low rate of hematologic complete responses (CRs). Twelve years ago, we began treating patients with AL amyloidosis with HDM/SCT. In the plasma cell malignancy multiple myeloma, this approach produces hematologic CRs and improves survival, but is not curative, as all patients eventually relapse. In AL amyloidosis, the relapse rate and long-term survival have not been studied, but early results are promising, with most centers reporting CR rates of ~40% and excellent survival in responding patients. To address the durability and long-term results of treatment with HDM/SCT, here we report on the outcome for AL amyloidosis patients treated at Boston Medical Center with HDM/SCT >10 years ago. The first autologous transplant took place on July 18, 1994 in two years, by July 18, 1996, 43 patients with AL amyloidosis without myeloma or other hematologic disease had been treated with HDM/SCT, receiving 100–200 mg/m² melphalan depending upon age and protocol. Of the 43 patients treated in this 2 yr period, 76% of the patients were male, 81% had a lambda monoclonal disease, and their median age was 52 (range, 29–71). In these first 43 patients, the 100 day peri-transplant mortality rate was 16%. Nineteen of the 43 patients (44%) achieved a hematologic CR after treatment. In annual followup, 4 of 19 patients (21%) eventually relapsed. Fourteen of 43 patients (33%) are still alive; 12 of 19 patients who achieved a CR (63%) are still alive, while only 2 of 34 patients who did not (6%) are still alive. Although there were fewer (8) patients with kappa clonal disease, they had a better outcome, with an 87% CR rate vs. 34% for lambda (P=0.006); 75% of the kappa patients are still alive, vs. 23% of the lambda patients (P=0.005). The median survival of all 43 patients is 4.7 years. Thus, treatment of AL amyloidosis patients with HDM/SCT produces a high CR rate that is durable and is associated with excellent 10 year survival, particularly for those patients achieving a hematologic CR and for patients with kappa clonal disease. Ongoing clinical trials of HDM/SCT, along with strategies to reduce morbidity and mortality and to improve the CR rate, incorporating additional cycles of HDM/SCT or new anti-plasma cell agents, appear to be well-justified by these results.