Tumor-Specific Clonotype, Metabolic Profile, and PET/CT in Predicting Chemotherapy Response in Patients With Relapsed or Refractory Diffuse Large B-cell Lymphoma

This pilot clinical trial studies tumor-specific markers (clonotype), blood tests, and positron emission tomography (PET)/computed tomography (CT) in predicting treatment response at different times during chemotherapy in patients with diffuse large B-cell lymphoma that has come back (relapsed) or does not respond to treatment (refractory). Studying samples of blood in the laboratory from patients during chemotherapy may help doctors learn more about the effects of treatment on cells and may help doctors determine whether patients are responding to treatment. PET/CT scan procedures are done at the same time with the same machine and the combined scans give more detailed pictures of areas inside the body than either scan gives by itself and may help doctors find out how well treatment is working.