Lost to Follow-up Rates Are Higher in Pediatric Than Adult Survivors, but Not By Transplant Type: A Report from the Center for International Blood and Marrow Transplant Research
Authors: Buchbinder David K. , Brazauskas Ruta , Bo-Subait Khalid , Ballen Karen K. , Hahn Theresa E. , John Tami D , Parsons Susan K , Hashmi Shahrukh K. , Khera Nandita , Wood William A. , Saber Wael 
Published: October 2019

Abstract
Introduction
Follow-up is an integral part of hematopoietic cell transplant (HCT) care which ensures accurate characterization of HCT-related outcomes as well as surveillance and intervention for complications. Despite the importance of follow-up of all HCT recipients at transplant centers, they may be lost to follow-up (LTFU). HCT recipients who are LTFU may be demographically or clinically distinct from HCT recipients who maintain regular center follow-up. Using population-based data from 17,550 adult and 4,279 pediatric HCT recipients from United States centers reported to the Center for International Blood and Marrow Transplant Research (CIBMTR), we characterize the incidence of, and predictors for, becoming LTFU.
Methods
The study included 2-year (yr) survivors of first allogeneic (10,367 adults and 3,865 children) or autologous (7,183 adults and 414 children) HCT for malignant and non-malignant disorders in the United States from 2002-2013 reported to the CIBMTR. LTFU was defined as a patient having missed 2 consecutive follow-up reporting periods. CIBMTR follow-up forms are collected annually for the first 6 yrs post-HCT and bi-annually thereafter. The cumulative incidence of LTFU HCT recipients was calculated. Marginal Cox models allowing adjustment for center effect were fit to evaluate risk factors for becoming LTFU among adults and pediatric allogeneic and autologous HCT survivors. Risk factors evaluated included: sociodemographic (age at HCT, sex, performance status, race, distance to center, income, health insurance, marital status) and disease/HCT-related (disease type, yr of HCT) factors.
Results
Among 2-yr allogeneic HCT survivors, the median age at the time of HCT was 49 yrs (range, 18-81) and 7 yrs (range, <1-18) for adult and pediatric recipients, respectively. Corresponding median follow-up was 75 months (mos) (range, 12-173) and 74 mos (range, 3-173). Health insurance coverage was public (23%) or private (64%) for adult recipients, and public (40%) or private (43%) for pediatric recipients. For 2-yr autologous HCT survivors, the median age at the time of HCT was 58 yrs (range, 18-82) and 4 yrs (range, <1-18) for the adult and pediatric recipients, respectively. Corresponding median follow-up was 76 mos (range, 3-174) and 73 mos (range, 6-173). Health insurance coverage was public (27%) or private (57%) for adult recipients, and public (48%) or private (39%) for pediatric recipients. The 10-year cumulative incidence of becoming LTFU among adult and pediatric allogeneic HCT recipients was 13% (95% CI, 12-14) and 25% (95% CI, 24-27), respectively. Among autologous HCT recipients, the 10-year cumulative incidence of becoming LTFU among adults and children was 15% (95% CI, 14-16) and 23% (95% CI, 19-28), respectively. (Figure 1) Among pediatric allogeneic HCT survivors, older age, non-white race, public or no insurance (referent: private), and earlier yr of HCT were significantly associated with increased LTFU risk. However, in adult allogeneic HCT survivors, younger age, non-malignant disease, public or no insurance (referent: private), living farther from the HCT center, and unmarried were significantly associated with higher risk of LTFU (Table 1). In pediatric autologous HCT survivors, males and Non-Hodgkin lymphoma (NHL)/Hodgkin lymphoma patients (referent: central nervous system tumors) were significantly associated with higher risk of becoming LTFU (Table 1), whereas for adult autologous HCT survivors, older age and multiple myeloma (referent: NHL) were significantly associated with decreased risk of LTFU.
Conclusions
The incidence of LTFU is significantly higher in pediatric than adult patients, with no difference between autologous and allogeneic HCT patients, regardless of age. We identified risk factors for LTFU that differed by age and HCT donor type. A national, comprehensive, risk-based approach to long-term follow-up focusing on minimizing the attrition in high-risk groups such as adolescent and young adult-aged HCT survivors and HCT survivors with non-private health insurance is needed. Future studies incorporating patient reported outcomes may help describe reasons for lack of long-term follow-up. Collection of accurate and meaningful epidemiologic and clinical data from all survivors can help develop and refine strategies to improve long-term outcomes of this population.

Disclosures
Parsons: Seattle Genetics: Research Funding.