Until now, direct comparisons of cancer survival between high-income and low-income countries have not generally been available. The information provided here might therefore be a useful stimulus for change. The findings should eventually facilitate joint assessment of international trends in incidence, survival, and mortality as indicators of cancer control.

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Summary A nationwide case-control study was conducted in New Zealand, to test hypotheses about the role of infections in the aetiology of childhood leukaemia. Children aged 0-14 years with leukaemia were matched on age and sex to controls selected from birth records. Case ascertainment was virtually complete and 121 (92%) of 131 eligible case families took part. The participation rate among the 303 first-choice eligible controls was 69%. Home interviews and serological tests were conducted. Adjusted relative risks were estimated by logistic regression. There was an increased risk of leukaemia in relation to reported influenza infection of the child during the first year of life (adjusted odds ratio 6.8, 95% confidence interval 1.8-25.7). This could be a chance finding due to multiple comparisons, and it should be tested elsewhere. Some key variables relevant to Greaves' hypothesis were not associated with B-cell precursor acute lymphoblastic leukaemia (numbers of infections and vaccinations, firstborn status, attendance at preschool groups), although a small effect could not be ruled out with a study of this size. Leukaemia risk was higher among children in poorer social circumstances, and this was true for all eligible children as well as for the participants.

The histories of exposure to sun through occupational, recreational and vacation activities of 595 patients with newly incident cutaneous melanoma excluding lentigo maligna and acral lentiginous melanoma, were compared to those of comparison subjects drawn randomly from the same population and matched for age, sex and province of residence in Western Canada. Significant increases in risk were seen with increasing amount of sun exposure through outdoor activities associated with recreation and vacations; activities likely to involve more intense sun exposure were associated with greater increases in risk. While a moderate amount of occupational exposure was associated with increased risk, greater occupational exposure resulted in no further increase; in men a decrease in risk was seen. These findings were independent of the effects of hair and skin colour, freckles, ethnic origin and socio-economic status. The results suggest that short-term exposure to unusually intense sunlight increases the risk of melanoma, while long-term constant exposure has no effect or may decrease risk. No simple relationship was seen between melanoma risk and total sunlight exposure. This study introduces new methods of assessing different types of sun exposure from retrospective data.