Lenalidomide, Dexamethasone, and Elotuzumab With or Without Cyclophosphamide in Treating Patients With Relapsed Primary Amyloidosis

Inclusion Criteria: * Biopsy-proven histochemical diagnosis of amyloid light-chain (AL) amyloidosis based on tissue specimens with Congo red staining or other histologic stain; thioflavin T or S, or crystal violet; tandem mass spec or immunohistochemistry (IHC) confirmation of immunoglobulin-derived amyloidosis is encouraged; cases in which histochemical confirmation is lacking need to be discussed with one of the Multiple Myeloma Research Foundation (MMRF) protocol chair/co-chairs * One prior line of therapy (defined as either one non-transplant regimen such as MelDex, Vel-Dex or CyBorD, one autologous stem cell transplant, or one regimen of non-transplant induction therapy followed by a single autologous stem cell transplant (without hematologic progression between induction and autologous stem cell transplant \[ASCT\]) * Measurable hematologic disease as defined by: * Serum differential free light chain concentration (dFLC, difference between amyloid forming \[involved\] and non-amyloid forming \[uninvolved\] free light chain \[FLC\]) \>= 50 mg/L) * Objective measurable (cardiac, renal or liver) organ amyloid involvement defined as follows (amyloid involvement of at least 1 required): * Mean wall thickness \> 12 mm on echocardiogram, with no other cardiac cause or an elevated NT-ProBNP (\> 332 ng/L) in the absence of renal failure or atrial fibrillation * Renal involvement is defined as proteinuria (predominantly albumin) \> 0.5 g/day in a 24-hour urine collection…