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Screen-detected and Interval Colorectal Cancers in England: Associations with Lifestyle and other Factors in Women in a Large UK Prospective Cohort

Blanks R, BurĂ³n Pust A, Alison R, He E, Barnes I, Patnick J, Reeves G, Floud S, Beral V, Green J.

Int J Cancer 2019 145(3):728-734.

Abstract
Faecal occult blood (FOB) – based screening programmes for colorectal cancer detect about half of all cancers. Little is known about individual health behavioural characteristics which may be associated with screen-detected and interval cancers. Electronic linkage between the UK National Health Service Bowel Cancer Screening Programme (BCSP) in England, cancer registration and other national health records, and a large on-going UK cohort, the Million Women Study, provided data on 628,976 women screened using a guaiac-FOB test (gFOBt) between 2006 and 2012. Relative risks (RRs) and 95% confidence intervals (CIs) were estimated by logistic and Cox regression for associations between individual lifestyle factors and risk of colorectal tumours. Among screened women, 766 were diagnosed with screen-detected colorectal cancer registered within 2 years after a positive gFOBt result, and 749 with interval colorectal cancers registered within 2 years after a negative gFOBt result. Current smoking was significantly associated with risk of interval cancer (RR 1.64, 95%CI 1.35-1.99) but not with risk of screen-detected cancer (RR 1.03, 0.84-1.28), and was the only factor of eight examined to show a significant difference in risk between interval and screen-detected cancers (p for difference, 0.003). Compared to screen-detected cancers, interval cancers tended to be sited in the proximal colon or rectum, to be of non-adenocarcinoma morphology, and to be of higher stage.

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