Trial type: Observational, non-therapeutic long-term safety follow-up. Interventions: No new treatment is given. Participants previously received genetically modified cell therapies (gene therapy/adoptive cellular therapy) engineered ex vivo with retroviral or lentiviral vectors, designed for durable gene expression after adoptive transfer. Mechanism of action: Stable integration/expression of therapeutic genes in transferred cells to mediate anti-cancer effects, the study monitors for delayed adverse events (e.g., insertional oncogenesis). Cells/pathways targeted: Vary by parent trial, commonly engineered immune effector cells (e.g., CAR‑T/TCR‑T) or gene‑modified hematopoietic cells targeting hematologic malignancies via antigen-recognition/cytotoxic pathways or corrected hematopoiesis.