Orthopedic Toxicities Among Adolescents and Young Adults Treated on DFCI ALL Consortium Trials.

Adolescent and young adult patients with acute lymphoblastic leukemia (ALL) have superior outcomes when treated on pediatric regimens. Pediatric ALL regimens rely heavily on corticosteroids and asparaginase and are known to increase the risk of osteonecrosis (ON) and fractures in children, particularly adolescents. Orthopedic toxicity among young adults treated on pediatric-inspired regimens is not well described. Here, we report the symptomatic orthopedic toxicities of patients aged 15-50 years treated on sequential Dana-Farber Cancer Institute (DFCI) ALL Consortium protocols. Among 367 patients with a median age of 23 years (range 15-50, 68% < 30 years), 60 patients were diagnosed with ON (5-year cumulative incidence (CI) 17%; [95% confidence interval 13-22]) and 40 patients experienced fracture (5-year CI 12% [95% CI 8-15]). Patients < 30 years were significantly more likely to be diagnosed with ON (5-year CI 21% vs. 8%, p=0.004). Patients treated more recently on pegaspargase-based protocols were significantly more likely to be diagnosed with ON compared to those treated on earlier trials with native E.coli asparaginase (5-year CI 24% vs 5%, p<0.001). Of the 54 ON events for which adequate information was available, surgery was performed in 25 (46%). Patients with ON had superior overall survival (OS) compared to those without (multivariable OS HR 0.15 [95% CI: 0.05-0.46], p=0.001; ON included as a time-varying exposure). Increased rates of orthopedic toxicity in late generation protocols may be driven by the pharmacokinetic drug interaction between pegaspargase and dexamethasone, leading to higher dexamethasone exposure.