Echoes from the past- changing associations between brain tumors and ethnicity

Background: cranial X radiation therapy was the standard of care for treating dermatological conditions until the 1960s, when its association to cancer and particularly high rates of brain tumors was discovered. This study examines associations found between incidence of brain tumor and ethnicity. Methods: This study analyzed two cohorts who underwent examination at age 17 and were followed by linkage to the national cancer registry. The first cohort included 376,336 participants born in 1948–1959 (when treatment with cranial X radiation was standard care for treating tinea capitis), and the second 474,923 participants born in 1960–1971. Results: In the first cohort, ethnicity was strongly associated with the incidence of brain tumor (BT), with higher incidence observed among patients with origins in North Africa or the Middle East. This effect was ablated in the second cohort, and a significant decrease in the rate of meningiomas was noted. Conclusion: The association of brain tumor with ethnicity was present only during the period when treatment with cranial X radiation was the standard of care for TC in Israel, therefore it is most likely that radiation exposure was a confounding factor, and that ethnic susceptibility for brain cancer was not causative in these cohorts.