Survival from childhood acute lymphoblastic leukaemia: the impact of social inequality in the United Kingdom.
BACKGROUND
Survival from childhood acute lymphoblastic leukaemia (ALL) has continued to improve in economically-developed regions of the world, but 20% of patients still die within 5-years of diagnosis. Treatment is prolonged and complex; and as survival rates plateau, factors relating to socio-economic status and/or treatment adherence are increasingly scrutinised as potentially important determinants of outcome.


METHODS
Predicated on the frame-work of the United Kingdom (UK) NHS, the relationship between socio-demographic factors and ALL survival is examined here using data from a large follow-up study conducted in the 1990s. One thousand five hundred and fifty nine children (0-14 years) diagnosed in England, Scotland &Wales during the era of the national UKALL XI randomized-controlled trial (RCT) were followed-up for an average of 15.9 years (20,826.3 person-years). Area-based deprivation scores and father's occupational social class at the time of the child's birth were used as markers of socio-economic status. Information on deaths was obtained from the NHS Information Centre for Health and Social Care. All children were included in the analyses, irrespective of RCT enrolment or participation in the founding epidemiological study (www.UKCCS.org).Survival effects were assessed using proportional hazards regressions models.


RESULTS
Survival varied with both area-based deprivation at diagnosis (hazard ratio (HR) 1.29; 95% confidence interval (CI) 1.05-1.57) and fathers occupational social class at birth (HR 1.12; 95% CI 0.97-1.29); the divergence beginning 6-9 months after diagnosis, and widening thereafter during home-administered therapy. The findings became more marked when analyses were restricted to those enrolled in UKALL XI (n = 1341). As expected, survival differences were also observed with sex, and age at diagnosis.


CONCLUSIONS
The existence of significant social disparities in ALL survival, which are not due to treatment accessibility, is of major clinical importance. Trends should be monitored and further research into potentially modifiable risk factors conducted.
Epidemiology & Genetics Unit, Department of Health Sciences, University of York, York YO10 5DD, United Kingdom. tracy.lightfoot@egu.york.ac.uk
T J
TJ
Lightfoot
W T
WT
Johnston
J
J
Simpson
A G
AG
Smith
P
P
Ansell
S
S
Crouch
E
E
Roman
S E
SE
Kinsey
D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000401:mortality*; D016016:Proportional Hazards Models; D012307:Risk Factors; D012737:Sex Factors; D012959:Socioeconomic Factors; D015996:Survival Rate; D006113:United Kingdom / Q000453:epidemiology