A curious correlation was reported yesterday at the annual meeting of the American Society for Therapeutic Radiology and Oncology: children who develop a common childhood brain cancer called medulloblastoma are more likely to have been born in the late summer or fall than the average U.S. population. The findings support earlier studies from Japan and Norway showing the same seasonal trend and lead scientists to wonder whether environmental factors that vary throughout the year--water pollutants, for example--may bear on brain development in the womb. "Children born in the fall would have been conceived the previous winter, and their brains would develop in the spring," says Edward Halperin, leader of the study from Duke University Medical Center. "What is happening during the spring more than at other times of the year that could explain the difference? Given other researchers' similar results, it's worth doing more research."
Halperin, working with Stephen George and statistician Dorothy Watson, examined the records of 122 medulloblastoma patients at Duke between 1983 and 1999, looking not only for links between birthdates but also gender, age, duration of symptoms before diagnosis and disease stage at diagnosis. They found that in addition to the late summer and fall connection, boys were far less likely to be diagnosed as quickly as girls after first showing symptoms. They attribute the lag to gender biases. "If a boy walks into a room, stumbles and knocks over a vase, the clumsiness may be brushed aside because he's a boy," Halperin points out.
This lag, though, did not mean that boys were diagnosed at a later disease stage. "We're all taught that an early diagnosis is the key to a cure when it comes to cancer and that it follows that early diagnosis must mean quickly diagnosed," Halperin adds. "However, with brain stem glioma, we've shown that a shorter duration of symptoms before diagnosis is related to a worse prognosis. With this study, we show that medulloblastoma behaves similarly." One explanation may be that with slow-growing tumors, the brain can adapt so that symptoms do not show up as rapidly.