Defining the Intensity of Conditioning Regimens: Working Definitions

TLDR

Defining conditioning regimen intensity has become a critical issue for the hemopoietic stem cell transplant (HSCT) community. The report proposes to define conditioning regimens in three categories: myeloablative (MA), reduced‑intensity (RIC), and non‑myeloablative (NMA). Regimens are categorized by cytopenia duration and stem cell support: MA causes irreversible cytopenia with mandatory support; NMA causes minimal cytopenia and may be given without support; RIC causes variable‑duration cytopenia, requires support but may not be irreversible, and the report assigns common regimens accordingly. Standardized classification will enable comparison across studies and interpretation of results.

Abstract

Defining conditioning regimen intensity has become a critical issue for the hemopoietic stem cell transplant (HSCT) community. In the present report we propose to define conditioning regimens in 3 categories: (1) myeloablative (MA) conditioning, (2) reduced-intensity conditioning (RIC), and (3) nonmyeloablative (NMA) conditioning. Assignment to these categories is based on the duration of cytopenia and on the requirement for stem cell (SC) support: MA regimens cause irreversible cytopenia and SC support is mandatory. NMA regimens cause minimal cytopenia, and can be given also without SC support. RIC regimens do not fit criteria for MA or NMA regimens: they cause cytopenia of variable duration, and should be given with stem cell support, although cytopenia may not be irreversible. This report also assigns commonly used regimens to one of these categories, based upon the agents, dose, or combinations. Standardized classification of conditioning regimen intensities will allow comparison across studies and interpretation of study results.