These are top 10 centers in US for cancer in general-you could research them more specifically for EC.
1. Sloan-Kettering: New York 2. MD Anderson: Houston 3. John Hopkins: Baltimore 4. Mayo Clinic: Rochester, MN 5. Dana-Farber: Boston 6. Duke Univ Med Center: Durham 7. Stanford Univ Hospital: Stanford 8. Univ Washington Med Center: Seattle 9. Univ of Chicago: Chicago 10. UCLA: Los Angeles 11. Roswell Park: Buffalo
Looks like Duke might be a good second option for you to explore in terms of location.