Total Body Irradiation Versus Chemotherapy-Only Conditioning in Autologous Haematopoietic Stem Cell Transplantation...

In the era of chimeric antigen receptor T-cell (CAR-T) therapy, there remains a role for autologous stem cell transplant (ASCT) for patients with large B-cell lymphoma (LBCL) without access to CAR T-cell therapy or who have late, chemosensitive relapse (>12 months). Typically, the ASCT conditioning regimen is chemotherapy only. Given the radioresponsiveness of LBCL, we retrospectively evaluated whether ASCT outcomes are improved with total body irradiation (TBI)-based conditioning compared to chemo-only conditioning.

We included patients with relapsed/refractory (r/r) LBCL who underwent ASCT at our centre (2012-2021). As TBI is generally offered only to younger patients, we excluded patients in the chemo-only group who were older than the oldest patient in the TBI group, leaving 56 patients in the final dataset (TBI: 19; chemo: 37).

The TBI cohort had more adverse features including male sex (89.5% vs 62.2%), relapse ≤12 months (52.6% vs 32.4%), and shorter time between diagnosis and ASCT (median: 11.7 vs 21.8 months). Two-year progression-free survival (PFS) was 58% (95% confidence interval [CI]: 39%-85%) and 67% (53%-84%) in TBI and chemotherapy cohorts, respectively. Two-year overall survival (OS) was 79% (63%-100%) and 80% (68%-95%) in TBI and chemotherapy cohorts, respectively. Multivariable hazard ratio (HR) of PFS failure (TBI vs chemo) was 1.35 (95% CI: 0.59-3.12). The HR of death was 1.33 (95% CI: 0.49-3.58). While conditioning regimen was not associated with PFS, positron emission tomography (PET) positivity at time of ASCT (HR: 6.97, 95% CI: 2.98-16.27, P < 0.001) was associated with PFS failure.

Despite the presence of more adverse features among patients treated with TBI, there was no difference in PFS or OS among patients that underwent chemo-only vs TBI-based conditioning. Though hypothesis generating, this suggests that TBI may be able to partially compensate for adverse fatures.