Incomplete follow-up in the National Cancer Institute's formaldehyde worker study and the impact on subsequent reanalyses and causal evaluations.

Three of us (G.M., A.Y., and P.M.) performed reanalyses of the National Cancer Institute cohort study on nasopharyngeal cancer (NPC) risk among formaldehyde exposed workers (Hauptmann et al., 2004). Both reanalyses (Marsh and Youk, 2005; Marsh et al., 2007) were published in this journal. However, the mortality follow-up performed by the NCI working group reported in two publications by Hauptmann et al. (2003, 2004) was later stated to be incomplete (Beane Freeman et al., 2009a,b). This incomplete follow-up may impact the validity of the results of our reanalyses. At this time, corrected estimates for solid cancer mortality risks including NPC as reported in Hauptmann et al. (2004) have not been provided as an erratum by the authors or reported anywhere else to our knowledge. We would like to inform readers about these issues and ask for a prompt corrigendum of the 2004 publication by the NCI working group since this study has played such a prominent role in causal evaluations.