Higher Incidence of Treatment-Related Toxicities in Non-Hispanic Patients Undergoing Therapy for Newly Diagnosed Pediatric Acute Lymphoblastic Leukemia on Dana-Farber Cancer Institute ALL Consortium Protocol 05-001

Background:  Risk-adapted treatment strategies have contributed to excellent outcomes in pediatric acute lymphoblastic leukemia (ALL);  however,  treatment-associated acute and long-term toxicities persist.  Therapy-associated toxicities of note in pediatric ALL are related to a treatment backbone that relies heavily on corticosteroids (prednisone and dexamethasone) and asparaginase (ASP).  The most frequently observed toxicities include, but are not limited to, serious infection, pancreatitis, thrombosis and bony morbidities including osteonecrosis (ON) and fracture.  Previous studies suggest that children of racial and ethnic minorities are at higher risk for treatment-associated toxicities.  We assessed the incidence of treatment-related toxicities in Hispanic and non-Hispanic patients undergoing treatment for pediatric ALL.

Patients and Methods:  Retrospective cohort study investigating the incidence of treatment-related toxicities including infection, allergy to ASP, pancreatitis, thrombosis and bony morbidities in Hispanic and non-Hispanic children and adolescents with newly diagnosed ALL undergoing therapy on Dana-Farber Cancer Institute (DFCI) ALL Consortium Protocol 05-001.  The ethnicity of each patient was designated at the time of study enrollment by research coordinators.  Descriptive statistics were calculated, mean +/- SD for continuous variables and frequency and percentages for categorical variables.  Toxicity rates were based on number of patients.  Comparison between groups was done by Chi-square test or FisherÕs exact test and p-value < 0.05 was considered significant.

Results:  Between 2005 and 2011, 794 children and adolescents (ages 1 – 18 years) were enrolled on Protocol 05-001, 730 of whom were evaluable for this investigation: 150 Hispanic (18%), 580 non-Hispanic (73%).  Sixty-four patients did not have ethnicity documented.  There was no significant difference in disease-risk group, age or gender between the two groups.  Weight was significantly higher in Hispanic patients (31.9 ± 24.4 kg in Hispanic and 26.9 ± 18.7 kg in non-Hispanic, p = 0.021).  There was no significant difference in the incidence of ASP-related toxicities (allergy, pancreatitis, thrombosis) between Hispanic and non-Hispanic patients.  There was no significant difference in the overall incidence of infection between the two groups (42% in Hispanic and 50% in non-Hispanic, p = 0.081).  Non-Hispanic patients had significantly higher rates of opportunistic infection (Pneumocystis pneumonia) than Hispanic patients (0.7% in Hispanic and 4% in non-Hispanic, p = 0.041).  A similar difference in the incidence of bacteremia between the two groups approached, but did not reach statistical significance (p = 0.052).  The overall incidence of fracture in all patients was 14.5% and was significantly higher in non-Hispanic patients (6% in Hispanic and 16.7% in non-Hispanic, p < 0.001).  The overall incidence of ON was 8.9% and was significantly higher in non-Hispanic patients (3.3% in Hispanic and 10.3% in non-Hispanic, p = 0.007). (Table 1)

Conclusion:  The incidence of opportunistic infections and bony morbidities was significantly higher in non-Hispanic patients undergoing treatment for pediatric ALL on the DFCI ALL Consortium Protocol 05-001.  The risk for, and impact of therapy-related toxicities varies by a patientÕs treatment tolerance, perhaps as a function of age and gender or as a result of disease biology or genetic polymorphisms affecting drug metabolism.  Additionally, non-biologic factors such as medication adherence and nutritional status may also contribute to toxicity incidence in patients undergoing treatment for pediatric ALL.  Prospective studies to further investigate our findings are warranted.

	All Patients, (N = 730)	Non-Hispanic, (N = 580)	Hispanic, (N = 150)	p-value
Overall Infection	353/730 (48.4%)	290/580 (50%)	63/150 (42%)	0.081
Bacteremia	289/730 (39.6%)	240/580 (41.4%)	49/150 (9.3%)	0.052
Opportunistic Infection	24/730 (3.3%)	23/580 (4%)	1/150 (0.7%)	0.041
Fracture	106/730 (14.5%)	97/580 (16.7%)	9/150 (6%)	<0.001
Osteonecrosis	65/730 (8.9%)	60/580 (10.3%)	5/150 (3.3%)	0.007
Thrombosis*	36/730 (4.9%)	26/580 (4.5%)	10/150 (6.7%)	0.271
Pancreatitis*	78/730 (10.7%)	60/580 (10.3%)	18/150 (12%)	0.559
ASP Allergy*	76/730 (10.4%)	57/580 (9.8%)	19/150 (12.7%)	0.310

*ASP-related toxicity