Abstract
AbstractSeasonal variation in the occurrence of several classes of cancer has been observed in the past. However, evidence for such trends in adult central nervous system tumors is scant. We have analyzed the monthly occurrence rates of glioblastomas as well as carcinomas metastatic to the brain in 6,154 neurosurgical patients in Toronto selected from the University Health Network neuropathologic database over a seven-year period (July 2001 to June 2008). The electronic repository was representative of the patient population in southern Ontario, and the case accession dates in the database reflected the onset patterns of the selected tumor groups. A modification to Nam's alternative method to the Roger test was developed to statistically quantify the differences. The results demonstrated significant cyclical occurrence rates of glioblastomas with seasonal peaks in March, June, September and December. Moreover, significant increases in the rates of carcinomas metastatic to the brain were found for January, April and August. Surprisingly, the monthly frequency for the two tumor groups resembled each other in peak/trough topology. Semiquantitative comparison of major histologic features between glioblastomas from a peak (March) and trough (November) month in the seven-year period was performed, revealing differences in the amount of perivascular lymphocytic inflammation. This novel observation may have profound implications for the understanding of the biology of adult central nervous system tumors.
Highlights
Understanding seasonal variations in disease occurrence can provide insights into pathogenesis which may have diagnostic and therapeutic implications
The current study presents further evidence for periodicity in the occurrence of glioblastomas and carcinomas metastatic to the central nervous system (CNS) over a sevenyear period in Toronto, Canada
Histologic evaluation of all glioblastoma cases from a peak (n = 33) and trough (n = 32) month demonstrated a significant increase in the amount of perivascular lymphocytic inflammation (P = 0.048) in the trough month (Figure 2)
Summary
Understanding seasonal variations in disease occurrence can provide insights into pathogenesis which may have diagnostic and therapeutic implications. The only reported observation of seasonal variation in adult malignant brain tumors was made from the Tumorzentrum Regensburg database in southeastern Germany [13]. Two groups of tumors were selected for review: glioblastomas and metastatic carcinomas. Tumors were grouped by month of surgery, and frequency was calculated relative to the total number of neurosurgical cases in that month. To investigate the biological basis of seasonal trends in glioblastomas, histopathology was compared between a peak (March) and a trough (November) month of frequency. Statistical analyses for seasonality studies are classically performed using the Roger test [15]. The major peaks in each trend were tested for significance against other monthly values, which were assumed to have minor variation relative to the yearly average. Statistical significance tests for histological analyses were performed using a two-sample, one-tailed Student’s t-test assuming equal variance, with P-values less than 0.05 considered significant
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