Competing interests: All authors have completed the ICJME uniform
disclosure form at www.icmje.org/coi_disclosure.pdf (available on
request from the corresponding author) and declare: HGP has received
research grants from the National Institute of Mental Health and the
National Cancer Institute; AAW has received research grants from the
National Cancer Institute and the American Cancer Society and a
Conquer Cancer Foundation of American Society for Clinical Oncology
Career Development Award; NLK received a research grant from the
National Cancer Institute; no financial relationships with any
organizations that might have an interest in the submitted work in the
previous three years; no other relationships or activities that could appear
to have influence the submitted work