Seasonal differences in the onset of childhood acute lymphoblastic leukemia are accompanied by different survivals

The results of the action of putative environmental carcinogenic stimuli on the organism were tested under natural conditions to see if they changed at different seasons. Chronopharmacological studies suggest that there are seasonal changes in response of an organism to certain hormones and different chemical and physical agents. Childhood acute lymphoblastic leukemia (ALL) seemed to be a good candidate to test for such differences since in this disease the time of clinical onset and time of diagnosis are not far apart. Furthermore, almost all these children die from this malignancy. A median follow-up of 27 months (range 1-5 years), revealed a time-related increase in survival: From a trough during November-January, there was a steady rise to a peak in August-October (44.1%, 45.7%, 66.7%, and 80.0%, respectively). It appeared that the pattern primarily was due to girls presenting at the time of diagnosis with a white blood cell count of less than 50,000 cells/mm3. The difference between the seasonal survival curves was not significant in the male patients, nor in the subgroups presenting with 50,000 or more cells. Recently, a similar circannual survival pattern was found in a subgroup of patients with advanced breast cancer. These seasonally changing survival patterns should be taken into account when composing homogenous trial groups for therapeutic experiments in ALL as well as in breast cancer.