International Liver Cancer Incidence Trends—Response

We thank Drs. McGlynn and London for their letter regarding our article (1), published in the November issue of Cancer Epidemiology, Biomarkers and Prevention. Our article was not a comprehensive review of international liver cancer epidemiology but as stated in the introduction, a specific examination of liver cancer incidence trends for registries with data covering the years 1993–2002 included in the International Agency for Research on Cancer's (IARC) Cancer Incidence in Five Continents (CI5) database (2). Therefore, we did not formally examine the trend in liver cancer incidence for the Qidong registry as data for this registry are not available after 1997 in CI5, although we did briefly note that incidence rates did not appear to show signs of a decline. Our main purpose in discussing the Qidong registry data was to highlight urban/rural differences in liver cancer incidence rates in China as well as the vast difference in rates, particularly among adults aged 30 years and older, between this rural region of China and other registries worldwide. We did emphasize in both the text and figure legend that the age-specific cross-sectional data presented for the Qidong registry were from 1993 to 1997 as opposed to data for the other registries which were from 1998 to 2002.

We appreciate Drs. McGlynn and London's mention of the article by Chen and colleagues (3) which reported that incidence rates in the Qidong registry between 1993–1997 and 1998–2002 decreased for both males and females and younger age groups. However, it is noteworthy that IARC includes only high-quality population-based cancer registry data in its CI5 database. The most recent volume (IX) of CI5 contains data for the period 1998 to 2002 and was released by IARC in 2007, one year after the publication by Chen and colleagues, yet these data from the Qidong registry were not included.

See the original Letter to the Editor, p. 384