Differences in colorectal cancer survival between European and US populations: the importance of sub-site and morphology § G. Gatta a, *, L. Ciccolallo a , R. Capocaccia b , M.P. Coleman c , T. Hakulinen d , H. Møller e , F. Berrino a , and the EUROCARE Working Group a Istituto Nazionale per lo Studio e la Cura dei Tumori, Division of Epidemiology, Via Venezian 1, 1-20133 Milan, Italy b Istituto Supenore di Sanita ´, Department of Epidemiology and Biostatistics, Viale Regina Elena 299, 1-00161 Rome, Italy c Cancer and Public Health Unit, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK d Finnish Cancer Registry, Liisankatu 21B, FIN- 00170 Helsinki, Finland e Thames Cancer Registry, King’s College London, Capital House, 42 Weston Street, London SE1 3QD, UK Received 17 February 2003; received in revised form 19 May 2003; accepted 16 June 2003 Abstract A previous study has shown a lower survival for colorectal cancer in Europe than in the United States of America (USA). It is of interest to examine the extent to which anatomical location and morphological type influence this difference in colorectal cancer survival. We analysed survival for 151 244 European and 53 884 US patients diagnosed with colorectal cancer aged 15–99 years during the period of 1985–1989, obtained from 40 cancer registries that contribute to the EUROCARE study from 17 countries, and nine Surveillance, Epidemiology and End-Results (SEER) registries in the USA. Cases included in the analysis were first pri- mary malignant tumours (ICD-O behaviour code 3 or higher). Relative survival was estimated to correct for competing causes of mortality. The Hakulinen–Tenkanen multiple regression approach was used to examine the prognostic impact of sub-site and ICD- O histology codes. Relative excess risks (RERs) derived from this approach estimate the extent to which the hazard of death differs from that in a reference region after adjustment for mortality in the general population. In order to explore geographical variation, we defined three groups of European registries within which survival rates were known to be broadly similar. The proportion of cases with unspecified sub-site was higher in Europe than the USA (10% versus 2%), but sub-site distributions were broadly similar in the two populations. With the exception of appendix, 5-year survival was 13–22% higher in the USA than in Europe for each anatomical sub-site. The proportion of non-microscopically-verified cases was higher in Europe than the USA (16 versus 3%). Adenocarcinomas arising in a polyp (ICD-O-2 8210, 8261, 8263) were more frequent in the USA than Europe (13 versus 2%). Five- year survival was higher in the USA than Europe for each morphological group, with the exception of non-microscopically-verified cases. When age, gender and sub-site were considered, RERs ranged from 1.52 to 2.40 for the European populations (with the USA as a reference). After inclusion of morphology codes, the range of RERs fell to between 1.28 and 1.86, mainly because of the high frequency of adenocarcinoma in polyps in the USA. This analysis suggests that the large survival advantage for colorectal cancer patients in the USA can only marginally be explained by differences in the distribution of sub-site and morphology. The main explanatory difference is the proportion of adenocarcinoma in polyps. # 2003 Elsevier Ltd. All rights reserved. Keywords: Relative survival; Population-based cancer registries; Colorectal cancer; Morphology; Sub-site; Europe; USA 1. Introduction Survival for most of the major adult cancers is higher in the United States of America (USA) than in Europe, especially among the oldest patients [1]. In the USA, 5- year relative survival for patients diagnosed with cancers of the colon and rectum during 1985–1989 were 60 and 57%, respectively, while in Europe the figs. were 48% for colon and 44% for rectum. These differences persisted in 0959-8049/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0959-8049(03)00549-5 European Journal of Cancer 39 (2003) 2214–2222 www.ejconline.com § Preliminary findings were presented at the 36th Annual Meeting of the Groupe pour 1 ‘Enregistrement du cancer dans les pays de Lan gue Latine (GRELL) in Neuchaˆtel, Switzerland, 24–25 May 2001. * Corresponding author. Tel.: +39-02-2390-3518; fax: +39-02- 2390-3522. E-mail addresses: gatta@istitutotumori.mi.it (G. Gatta), cicco- lallo@istitutotumori.mi.it (L. Ciccolallo), henrik.moller@kcl.ac.uk (H. Møller), berrino@istitutotumori.mi.it (F. Berrino).