Comparative effectiveness analysis of different salvage therapy intensities used for diffuse large B-cell lymphoma in Northern or Southern Alberta: an instrumental variable analysis.

To date, no clinical trial has addressed salvage therapy intensity for relapsed/refractory diffuse large B-cell lymphoma (DLBCL). We sought to determine whether the more intensive salvage chemotherapy approach used in Southern Alberta (SAB) compared to the conventional dose salvage approach used in Northern Alberta (NAB) affects the rates of autologous stem cell transplant (ASCT) and survival in patients with relapsed DLBCL. Using instrumental variable analysis, we examined 147 consecutive patients with relapsed/refractory DLBCL from 2004 to 2010 who received salvage therapy in SAB (n = 70) or NAB (n = 77). Patients treated in SAB had higher rates of: salvage chemotherapy response (85.0% vs. 54.0%, p = 0.001), ASCT (61.4% vs. 41.6%, p = 0.016) and 4-year overall survival (41% vs. 20%, p = 0.002) than those in NAB, respectively. This study supports the hypothesis that selective use of intensive salvage chemotherapy leads to higher rates of ASCT and survival in this population.