Her record-setting time came 10 years ago this month.
Cancellation comes after a runner died during last week's half-marathon.
Deena Kastor is ranked second.
Patrick Makau and Edna Kiplagat are at the top of the list.
Fast times are expected as a result.
The famous marathon will be broadcast live again.
Brett Gotcher and Nick Arciniaga lead the way on the men's side.
He perished in a car accident.
It will be a comeback race for the 33-year-old Kenyan.
He says he's in top shape still.