Subsequent malignant neoplasms in pediatric cancer patients treated with and without hematopoietic SCT.

Pediatric cancer patients are at increased risk of subsequent malignant neoplasms (SMNs). However, little is known about the contribution of hematopoietic SCT (HSCT) to the development of SMNs. The objective of this study was to compare the incidence of SMNs in a population cohort of childhood cancer survivors treated with and without HSCT. A cohort of 7986 children (age 0-14 years) diagnosed with cancer in the province of Ontario, Canada between 1985 and 2009 was identified in POGONIS (Pediatric Oncology Group of Ontario Networked Information System), a population-based active cancer registry, and linked to a clinical HSCT database. Among this cohort, 796 patients had an HSCT as part of their primary treatment. Of the 375 allogeneic HSCT patients, 14 (3.7%) developed a SMN at a median follow-up of 12.3 years (range: 2.0-22.9 years). Of the 421 autologous HSCT patients, 8 (1.9%) developed a SMN at a median of 4.5 years (range: 1.3-14.3 years). Of the 7190 patients who did not receive an HSCT, 160 (2.2%) developed a SMN at a median follow-up of 6.8 years (range: 0.0-24.9 years). The 15-year cumulative incidence of SMN was 3.1% among the allogeneic HSCT group, 2.5% among the autologous group and 2.3% in the non-HSCT group. The cumulative incidence curves for the allogeneic HSCT and non-transplant groups only diverged after ~15 years from primary diagnosis. Our findings further corroborate the observation that children who undergo allogeneic HSCT are at a significantly increased risk of developing SMN compared with pediatric cancer survivors treated without HSCT.

Late mortality after hematopoietic SCT for a childhood malignancy.

Hematopoietic SCT (HSCT) has been used as a curative therapy for pediatric malignancies. Survivors of HSCT are at risk for disease recurrence, late morbidity and mortality. We assessed late mortality (≥2 years post-HSCT) in a population-based cohort of children who underwent HSCT for a malignancy. Mortality outcomes were determined by linking a clinical transplant database with the Canadian province of Ontario's pediatric cancer mortality files. Seven hundred and fifty-four children underwent HSCT (371 allogeneic, 383 autologous). Of the 479 (63.5%) who were alive ≥2 years post HSCT, 98 (20.5%) suffered a late death. Late mortality in the allogeneic HSCT group was 14.9% (median follow-up 10.0 years; range: 2.0-25.6 years), mainly due to relapse of the primary malignancy (64.7%). Chronic GVHD and second malignancies were not major causes of late mortality. A total of 25.5% suffered a late death following autologous HSCT (median follow-up 6.7 years; range: 2.0-22.2 years). Recurrence of the primary malignancy accounted for 87.5% of these deaths. Recurrence of the primary malignancy is the predominant cause of late mortality after HSCT. In contrast to studies of adult patients, non-relapse mortality is less common in children, and death due to chronic GVHD and secondary malignancies is uncommon.