Magnetic field exposure and long-term survival among children with leukaemia

We examined the association between magnetic field (MF) exposure and survival among children with acute lymphoblastic leukaemia (ALL) treated at 51 Pediatric Oncology Group centres between 1996 and 2001. Of 1672 potentially eligible children under treatment, 482 (29%) participated and personal 24-h MF measurements were obtained from 412 participants. A total of 386 children with ALL and 361 with B-precursor ALL were included in the analysis of event-free survival (time from diagnosis to first treatment failure, relapse, secondary malignancy, or death) and overall survival. After adjustment for risk group and socioeconomic status, the event-free survival hazard ratio (HR) for children with measurements >= 0.3 mu T was 1.9 (95% confidence interval (CI) 0.8, 4.9), compared to < 0.1 mu T. For survival, elevated HRs were found for children exposed to >= 0.3 mT (multivariate HR = 4.5, 95% CI 1.5 - 13.8) but based on only four deaths among 19 children. While risk was increased among children with exposures above 0.3 mu T, the small numbers limited inferences for this finding.