Decreased survival for childhood leukaemia in proximity to TV towers

Hocking B, Gordon I,

Presented at the Annual Scientific Meeting of the Royal Australasian College of Physicians in Adelaide, SA, 2-5 May 2000

Objective: In a previous study we reported an increased risk of childhood leukaemia in municipalities proximate to TV towers in north Sydney compared with more distant ones (Hocking B Gordon I Hatfield G Grain H. Cancer incidence and proximity to TV towers Med J Aust 1996; 165: 601-605). The rate ratio for incidence, comparing the inner ring of municipalities to the outer ring, was 1.55 (95% confidence interval 1.00 - 2.41) and for mortality the rate ratio was 2.74 (95% confidence interval 1.42 - 5.27).

The objective of the current study was to analyse the survival experience of the cases in detail, to determine whether there are differences between the two populations.

Design and Outcome Measures: Survival data on cases diagnosed from 1972-93 were analysed. Data on all cases who survived for less than one month were verified by the NSW cancer registry and one case diagnosed at autopsy excluded. Data were described by Kaplan-Meier curves. The log-rank and Wilcoxon tests were used to compare the two groups. Cox's proportional hazards model was used to adjust for confounders.

Results: There were 123 diagnosed cases of acute lymphatic leukaemia (ICD-9 204.0) of which 29 (16 deaths) were in the inner ring of municipalities and 94 (34 deaths) were in the outer ring. We found a significant difference in survival (log rank: P = 0.03; Wilcoxon: P = 0.05). The 5 year survival in the inner ring of municipalities was 55% and in the outer ring 71% (inner 23% worse); at 10 years the survival was 33% and 62% respectively (inner 47% worse). After adjustment for the potential confounders using Cox's model, the mortality rate ratio comparing the inner ring with the outer ring was found to be 2.1 (95% confidence interval: 1.1 - 4.0). We were not able to control for cytogenetic abnormalities.

Conclusion: There was an association between proximity to the TV towers and decreased survival, among cases of childhood leukaemia.