2.2. Study demographics and clinical data
Demographic data and clinical information were collected. Clinical information collected includes age at diagnosis, gender, stage of the disease, number of sites of extra-nodal involvement, serum LDH at diagnosis, performance status and remission status during transplantation. Disease staging was assessed according to the Ann Arbor classification. Clinical staging was performed using positron emission tomography or computed tomography scanning of the neck, thorax, abdomen, and pelvis; bone marrow biopsy; cerebrospinal fluid examination if available; and other tools, such as magnetic resonance imaging if available.
Remission status was assessed using the International Working Group criteria. International prognostic index (IPI) (which includes age, performance status, stage, extranodal involvement, and LDH level) were used as clinical prognostic factors. Index values of 0 and 1 are classified as low risk (L), 2 as low-intermediate risk (L/I), 3 as high-intermediate risk (H/I) and both 4 and 5 factors as high risk (H). The risk groups were further categorized into 2 groups; where an IPI score of 0-2 was defined as low risk, whereas 3-5 was considered high risk.
Other transplant data such as total CD 34+ stem cell dose infused, type of conditioning regimens, days to engraftment, transplant related complications and outcome were also recorded. Patients were followed up until December 2017 for the incidence of relapse and death. OS was measured from the date of diagnosis until death from any cause, with surviving patients censored at the last follow-up date. EFS was defined from the date of diagnosis to the date of disease progression, relapse or death from any cause.