Cohort studies of etiology and survival after cancer: the unique needs for uninterrupted funding.

The existing prospective cohorts are providing key data that are guiding public health and clinical practice in many different areas. The existing cohorts can also provide the biological specimens and data to address genetic determinant of cancer now, rather than in a decade, and at far less cost than that proposed for a new national U.S. cohort. Review and funding mechanisms are needed to avoid disruption in follow-up and the associated damage to existing cohorts.