The Influence on Survival of Season of Onset of Childhood Acute Lymphoblastic Leukemia (All)

Abstract

Rhythmicity has been found to be an important characteristic of leukocytes. We tested, therefore, whether rhythmicity could be found to be reflected in one or more of the developmental stages of childhood acute lymphoblastic leukemia. The patient material comprised 205 children 96 girls and 109 boys) whose disease was diagnosed in Israel during the years 1976-1981. Their mean age was 5.9 years ± 3.94. No seasonal onset of disease was found, either in the whole group or in subgroups divided by sex or lymphocyte surface markers. Survival analyses however, revealed that the season of diagnosis influenced survival. Excluded from the study were 9 cases (4.4%) due to lack of some items. The follow-up period was between 1 and 72 months (median 26 months). It appeared that the life table curves were running in their temporal order, each following curve representing a consecutive 3-month period. The difference between the curves was statistically significant (p = 0.025/0.009). The survival percentages at the end of the follow-up increased steadily, from a trough during November-January (56.5%) to a peak in August-October (80.0%). Analysis by sex and white blood cell (WBC) count showed that the difference between the life table curves was primarily due to girls presenting less than 50,000 cells per cumm (n = 73, p = 0.005/0.0028). The survival percentages in the same order as mentioned earlier were: 47.1%, 68.4%, 89.5% and 94.4%. The steady rise in the different female time series suggests a circannual pattern. In the male series no temporal order could be detected nor did the difference between seasonal survival reach a level of significance. The significance of the participation of natural environmental factors in causing the seasonal variations in malignancy is discussed.