Trends in Late Mortality and Life Expectancy after Autologous Blood or Marrow Transplantation (BMT) Performed over Three Decades - a BMT Survivor Study (BMTSS) Report

Background: Advances in therapeutic and supportive care strategies have led to increasing use of autologous BMT to ensure durable disease-free survival in patients with hematologic malignancies. However, autologous BMT recipients carry a high burden of morbidity. The cumulative effect of autologous BMT and the long-term morbidity on life expectancy remains unknown. Further, the impact of changes in transplant practice (older age at BMT, increasing proportion of patients undergoing autologous BMT for plasma cell dyscrasias [PCD], increasing use of peripheral blood stem cells [PBSCs] and decreasing use of total body irradiation [TBI]) on late mortality and life expectancy remains unknown. We determined trends in life expectancy and cause-specific late mortality after autologous BMT performed over a 33y period (1981-2014) using the resources offered by BMTSS - a multi-institutional collaborative designed to examine late morbidity and mortality after BMT.

Methods: This retrospective cohort included 4,702 individuals who lived ≥2y after autologous BMT performed between 1981 and 2014 at three transplant centers. We examined trends in life expectancy and late mortality over four eras: 1981-1999; 2000-2005; 2006-2010; 2011-2014. Endpoints included all-cause, recurrence-related mortality (RRM) and non-recurrence-related mortality (NRM) and projected reduction in life expectancy. Information on vital status and cause of death was obtained from National Death Index (NDI) Plus program and Accurinct databases. End of follow-up was 04/19/2021.

Results: Median age at BMT was 53y (range, 0-78); 58.7% were male, 67.8% non-Hispanic white. Median follow up after BMT was 9y (range, 2-36). PCD was the most common indication for autologous BMT (42.3%). PBSCs were used for 91.6% of the transplants and TBI was used for conditioning in 23.1% of the patients. Across the four eras, the median age at BMT increased (40y→58y), as did the proportion of patients receiving autologous BMT for PCD (13.7%→60.0%) and the proportion of patients receiving PBSCs as the stem cell source (66.6%→99.5%). There was a dramatic decline in the proportion of patients conditioned with TBI (56.4%→5.2%), and those transplanted for acute myeloid leukemia/ myelodysplastic syndrome (AML/MDS) (15.4%→0.2%). Conditional on surviving ≥2y after autologous BMT, patients experienced a 25.8% reduction in life expectancy, representing 7.0y of life lost. In an analysis adjusted for all relevant demographic and clinical predictors and restricted to 5y of follow-up, the years of life lost declined across the four eras from 5y to 1.6y (Fig 1) The adjusted hazard of all-cause mortality also declined over the four eras (reference: 1981-1999; hazard ratio [HR]_2000-2005=0.77; 95%CI=0.7-0.9; HR _2006-2010=0.62; 95%CI=0.5-0.7; HR _2011-2014=0.5; 95%CI=0.4-0.6; P _trend <0.0001) (Fig 2). Mediation analysis revealed that the reduction in late mortality was evident among those transplanted for Hodgkin lymphoma (HL) or PCD, and among those who did not receive TBI . The 30y cumulative incidence of NRM (29.2%) was higher than that RRM (23.8%) (Fig 3). The adjusted hazard of RRM declined over the four eras (reference: 1981-1999; HR _2011-2014=0.55; 95%CI=0.4-0.7, P _trend: <0.0001). Cause-specific late mortality declined for mortality related to infection (P _trend <0.0001), subsequent malignant neoplasms (P _trend=0.01), cardiovascular disease (P _trend=0.001), and renal disease (P _trend=0.0002), but not for pulmonary disease (P _trend=0.3).

Conclusions and Relevance: Late mortality among autologous BMT recipients has declined over a 30y period, likely due to changes in transplant practice (reduction in use of TBI) and improvement in disease-specific therapeutic strategies (newer therapeutic options for PCD and reduction in dose/volume of radiation for HL). Continued efforts need to focus on mitigation strategies for disease recurrence, subsequent neoplasms, infections, and cardiovascular, renal and pulmonary disease in this population.

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