Hospitalizations Among Adult Survivors of Childhood Cancer Treated with Stem-Cell Transplantation

Background: Hematopoietic stem cell transplantation (HSCT) has become a standard component of therapy for several pediatric malignancies. As HSCT improves survival among those afflicted with these malignancies, and supportive care advances diminish the acute toxicities of HSCT, the risk for late complications in survivors is of increasing concern.  We have recently shown that nearly 80% of patients survive beyond 2-years after HSCT.  However, knowledge regarding the burden of morbidity after HSCT once survivors reach adulthood is sparse. Frequency of hospitalizations can serve as a proxy measure of morbidity in this population.

Objectives: To assess the number of hospitalization episodes in long-term adult survivors of childhood malignancies treated with HSCT in a tertiary center.

Methods: We used record linkage between the SickKids’ clinical transplant database, the Canadian Province of Ontario’s pediatric cancer registry (POGONIS) and health care utilization data housed at the Institute for Clinical Evaluative Sciences (ICES). The study population included all adult survivors (age ≥ 18 years) of childhood cancer diagnosed  prior to age 18 years between 1986 and 2005, who had received cancer therapy that included an allogeneic or autologous HSCT at SickKids, and who had survived more than 5 years from transplant. Hospitalizations were captured from the later of each survivor’s 18^thbirthday or 5 years after HSCT until the end of the follow-up period (Dec 2011) or death.

Results: The cohort consisted of 242 long-term adult survivors who were followed for a mean of 12.3 years. Of these, 148 underwent allogeneic and 86 autologous HSCT. Mean age at HSCT for the allogeneic group was 11.5 y (SD: 4.7) and 11.0 y (SD: 5.3) for the autologous group. A total of 262 hospitalizations were documented in adults post allogeneic HSCT, representing a rate of 0.15 hospitalizations per follow-up year. Univariate analysis revealed that age >10 years at cancer diagnosis (RR=3.53, 95% CI: 2.34-5.33), age >10 years at HSCT (RR=5.88, 95% CI: 2.89-11.85), and female gender (RR=1.70, 95% CI: 1.33-2.18) were associated with an increased rate of hospitalization.  The underlying diagnosis, ALL vs. AML was not associated with increased rate of hospitalization despite the use of total body irradiation among ALL patients. A total of 106 hospitalizations were documented in adults post autologous HSCT, representing a rate of 0.09 hospitalizations per follow-up year. Age >10 y-o at time of HSCT (RR=2.29, 95% CI: 1.29-4.04) and female gender (RR=1.70, 95% CI: 1.15-2.52) were associated with increased rate of hospitalization.

Conclusions: We have identified risk factors for hospitalization in adults who underwent HSCT during childhood. Age > 10 years at time of HSCT and female gender were associated with increased risk for hospitalization. Our future studies focus on length of stay and the indications for these hospitalizations.