Safety and Efficacy of Once Weekly Subcutaneous Bortezomib in Advanced Stage AL Amyloidosis

Background:

Intravenous bortezomib (BTZ) based therapy is effective for AL amyloidosis, although cardiac toxicity is a concern in advanced stage patients (pts). Survival in AL amyloidosis is dependent on hematologic and cardiac organ response emphasizing the need for safe and effective treatments. Staging systems to identify high cardiac risk pts developed by Dispenzieri et al JCO 22.18 (2004): 3751-3757 and revised by Kumar et al JCO 30.9 (2012): 989-995 can be used to guide therapy. Since January 2011, our institutional preference has been to treat plasma cell disorder patients with subcutaneous (SC) once weekly BTZ and have eliminated requirement for intravenous hydration. Considering the historically poor outcome of high cardiac risk AL amyloid pts with conventional therapy, we did not exclude them from weekly SC bortezomib and report safety and efficacy data here.

Methods:

After IRB approval, we reviewed our plasma cell disorder registry and identified 40 pts with AL amyloidosis who received weekly SC BTZ as initial therapy between January 2011 and June 2014. Review of the electronic medical record was used to confirm details of BTZ based regimens, response to treatment according to consensus criteria (Palladini et al. JCO (2012): 4541-4549.), and adverse events including neuropathy and cardiac toxicity graded via the NCI CTCAE version 4.0. We ascribed advanced cardiac stage to pts who were stage 3 by the 2004 staging and 3 and 4 by the 2012 staging. Six pts were excluded from hematologic response assessment as the difference between the involved and uninvolved free light chains was less than 50 mg/L at baseline.

Results:

Out of the 34 evaluable pts, 18 (53%) and 23 (68%) were found to be advanced cardiac stage by the respective staging systems and 1 of these pts died of ventricular tachycardia arrest about 8 hours after initial 1 mg/m2 bortezomib dose with 8 mg of dexamethasone. Additional toxicity included grade 4 ventricular tachycardia in 1 patient after the fifth cycle of BTZ although not in close relation to the BTZ dose. Neurologic toxicity attributed to BTZ was seen in 4 pts (10%) with 3 grade 1 and 1 grade 3. Six deaths occurred in SC BTZ treated pts and all were in advanced cardiac stage pts. Two advanced cardiac stage pts successfully underwent high dose melphalan and autologous stem cell transplant. Hematologic responses are listed in the tables. All patients received corticosteroid.

Discussion:

Only 2 pts experienced cardiac toxicity and 1 was in close temporal relation to the BTZ dose but resulted in death. The responses seen with weekly SC BTZ in advanced cardiac stage AL amyloidosis are reasonably consistent with those seen with intravenous dosing although small patient numbers limit this comparison. Hematologic response in pts treated with BTZ and corticosteroid alone can support a response adapted therapeutic approach. Two advanced cardiac stage pts were able to undergo high dose melphalan after improvement in their cardiac status with BTZ based therapy. Once weekly SC BTZ based therapy was safe and effective treatment for AL amyloidosis even in high cardiac risk pts.