Brentuximab Vedotin and Bendamustine for the Treatment of Relapsed or Refractory Follicular Lymphoma

Inclusion Criteria: * Histologically or cytologically confirmed relapsed or refractory follicular CD30+ non-Hodgkin lymphoma (NHL) (included in this category are follicular grade I, II, IIIa). CD30 positivity \> 1% (tumor cells or surrounding peripheral microenvironment) * Patients must have measurable disease by computed tomography (CT) or positron emission tomography (PET) scan, with one or more sites of disease \>= 1.5 cm in longest dimension * Relapsed or refractory disease after at least 1 prior regimen, defined using the 2014 Lugano classification * Eastern Cooperative Oncology Group (ECOG) performance status =\< 2 (Karnofsky \>= 60%) * Life expectancy of greater than 3 months * Leukocytes \>= 2,500/mcL * Absolute neutrophil count \>= 1,000/mcL * Platelets \>= 50,000/mcL * Hemoglobin \>= 8 g/dL * Total bilirubin =\< 1.5 x institutional upper limit of normal (ULN) (however, patients with known Gilbert disease who have serum bilirubin level =\< 3 x ULN may be enrolled) * Aspartate aminotransferase (AST) (serum glutamic-oxaloacetic transaminase \[SGOT\])/alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase \[SGPT\]) =\< 3 x ULN (AST and/or ALT =\< 5 x ULN for patients with liver involvement) * Alkaline phosphatase =\< 2.5 x ULN (=\< 5 x ULN for patients with documented liver involvement or bone metastases) * Creatinine clearance \>= 30 mL/min/1.73 m\^2 by Cockcroft-Gault * Institutional normalized ratio (INR) and partial thromboplastin time (aPTT) =\< 1.5…