Relapsed Malignant Blood Cancer After Allogeneic Hematopoietic Stem Cell Transplantation

Background: * Cancer relapse is a significant clinical problem following allogeneic hematopoietic stem cell transplantation (allotransplant), affecting up to half of all patients. Effective treatment options are extremely limited and, for most cancers, rarely curative. * Several Clinical Center (CC) protocols are evaluating treatment for post-allotransplant relapse. Relapse often progresses quickly; patients require rapid assessment of protocol options in order to expedite initiation of treatment. * Basic information is needed to improve management of relapse after allotransplant clinical information regarding risk of relapse and cancer behavior after allotransplant, and information on the biology of relapse after allotransplant in order to identify risk factors, target prevention strategies, detect early relapse and develop effective treatments. Objectives: Primary Objective: To provide a mechanism for systematic, comprehensive evaluation of individuals with relapsed hematologic malignancy after allotransplant and, if available, their donors, to streamline identification of protocol options, enrollment and initiation of therapy. Eligibility: 1. Individuals who have received allotransplant treatment for hematologic malignancy ("Recipient-Subjects"). Analyses (secondary aims) will consider two comparison cohorts: 1. Relapse Cohort: Cancer progression, relapse or persistently stable (unremitting) disease 2. Remission (Control) Cohort: Cancer response or remission at/after Day 100 2. Individuals who are being enrolled on Clinical Center protocols to undergo allotransplant therapy for hematologic malignancies and are being evaluated at the Clinical Center for planned allotransplantation. (Recipient-Subjects) 3. Related donors of eligible allotransplant recipients ("Donor-Subjects") Design: 1. Recipient-Subjects will have clinical and research evaluations at baseline and three and six months post-allotransplant, at six-month intervals through three years post-allotransplant, then yearly. Evaluation after relapse treatment response and for new protocol options is permitted. 2. Donor-Subjects will be enrolled at the time of their clinical evaluation and cell collection for Recipient-Subject therapy. Return evaluation for additional clinical product collection is permitted. 3. Accrual Ceiling: 500 consented subjects (350 Recipient-Subjects and 150 Donor-Subjects) over 5 years, averaging 70 Recipient-Subjects and 30 Donor-Subjects enrolled per year.