Seasonal variation in the incidence of primary CNS lymphoma

Primary CNS lymphoma is a rare and aggressive cancer that can develop in immunocompetent individuals, but little is known about risk factors and causes of disease. Previous studies have demonstrated seasonal patterns for lymphomas and brain tumors. This study examined the seasonal incidence pattern for primary CNSlymphoma.

A retrospective review was performed for patients diagnosed with primary CNS lymphoma from 2000 through 2018 at our tertiary referral center. A total of 156 patients were categorized based on month of symptom onset, month of diagnosis, and month of recurrence if they experienced a relapse of their disease. The distributions were then analyzed for seasonal patterns.

There was a significant, bimodal seasonal incidence pattern based on month of symptom onset (P < .001), with peaks in July (n = 19) and December (n = 23) and troughs in March (n = 4) and September (n = 5). There were no significant differences in patients' sex, age at presentation, length of follow-up, and progression-free survival across months. There were no seasonal patterns based on month of diagnosis (P = .450) or month of disease recurrence (P = .572).

The incidence of primary CNS lymphoma has bimodal peaks in midsummer and early winter, which could provide insight into causative agents and mechanisms of disease.