Effect of Severe Hypoalbuminemia on Myelosuppression and Other Toxicities of High Dose Melphalan and Autologous Stem Cell Transplantation in AL Amyloidosis Patients

Background: Treatment of AL amyloidosis with high dose intravenous melphalan followed by autologous stem cell transplant (HDM/SCT) is effective in inducing hematologic and clinical remissions associated with prolonged survival. The major toxicities are myelosuppression and GI side effects. Studies have shown that ~75% of melphalan in the blood is bound to plasma proteins, with ~25% free. We hypothesized that AL patients with severe nephrotic syndrome and profound hypoalbuminemia might have a higher fraction of free melphalan, a higher effective dose, and greater toxicity of treatment.

Methods: Patients with AL amyloidosis and severe hypoalbuminemia, defined as serum albumin level of < 2 g/dL, treated from 2011 to 2013, were studied retrospectively. The stem cell transplant database was queried for dose of HDM, treatment-related complications, and days of neutrophil and platelet engraftment after SCT.

Results: Of 71 patients with AL amyloidosis who underwent HDM/SCT between Jan 2011 and Dec 2013, 12 patients had severe hypoalbuminemia. Of these, 5 received full HDM at 200 mg/m² and 7 received modified HDM at 140 mg/m². All patients received GCSF mobilized peripheral blood stem cells following HDM, with a median stem cell dose of CD34+ cells 8.1 x 10⁶/kg (range, 4.0 to 12.2). The median time to engraftment of neutrophils was 11 days, and not statistically different based upon melphalan dose. The median time to platelet engraftment was 13 days, and also did not differ significantly by dose. These times were similar to controls without severe hypoalbuminemia. Grade 4 toxicities were observed in 2 of 7 patients with modified HDM/SCT and 1 of 5 patients with full HDM/SCT.

Conclusions: These data suggest that patients with severe hypoalbuminemia do not have more prolonged myelosuppression or increased non-hematologic toxicities compared to other patients. In this retrospective study, we did not measure free melphalan concentrations in the blood. However, these data suggest that patients with severe hypoalbuminemia do not require adjustment of melphalan dosing.