Simplify the following text for a Grade 6 native English-speaking person.
Original: A founding paper of cancer epidemiology was the work of Janet Lane-Claypon , who published a comparative study in 1926 of 500 breast cancer cases and 500 control patients of the same background and lifestyle for the British Ministry of Health .
Simplified: She published a comparative study in 1926 . It was about 500 breast cancer cases and 500 control patients .