[1] Univ Calif San Diego, Sch Med, La Jolla, CA 92093 USA
[2] Univ Texas Southwestern Med Ctr Dallas, Dept Pediat Hematol & Oncol, Dallas, TX 75390 USA
[3] Univ Calif San Diego, Dept Family Med & Publ Hlth, La Jolla, CA 92093 USA
[4] Univ Calif San Diego, Moores Canc Ctr, 3855 Hlth Sci Dr 0901, La Jolla, CA 92093 USA
[5] Oregon State Univ, Sch Social & Behav Hlth Sci, Corvallis, OR 97331 USA
[6] Univ Massachusetts, Dept Biostat & Epidemiol, Amherst, MA 01003 USA
[7] Univ Calif San Diego, Dept Obstet Gynecol & Reprod Sci, La Jolla, CA 92093 USA