[1] Columbia Univ, Joseph L Mailman Sch Publ Hlth, Dept Epidemiol, New York, NY 10032 USA
[2] Columbia Univ, Herbert Irving Comprehens Canc Ctr, New York, NY 10032 USA
[3] Columbia Univ, Coll Phys & Surg, Dept Med, New York, NY 10032 USA
[4] Columbia Univ, Joseph L Mailman Sch Publ Hlth, Dept Hlth Policy & Management, New York, NY 10032 USA
[5] Univ Penn, Sch Med, Dept Obstet & Gynecol, Philadelphia, PA 19104 USA
[6] Univ Toronto, Sunnybrook Hlth Sci Ctr, Toronto, ON, Canada
[7] Univ Penn, Sch Med, Dept Biostat & Epidemiol, Philadelphia, PA 19104 USA