2 new articles on colorectal cancer screening in NEJM last month.
1. retrospective review of the nurses’ health study and the health professionals follow-up study (not a randomized controlled trial), of 90K people followed 22 years (see DOI: 10.1056/NEJMoa1301969). results:
— total of 1815 incident cancers and 474 colorectal cancer deaths
–with any lower endoscopy done, 43% fewer colorectal cancers in those who had a polypectomy for adenoma, 40% fewer in those with negative sigmoidoscopy, and 56% fewer in those with negative colonoscopy. data consistent for men and women.
–for proximal lesions (prior data suggested less efficacy of screening on proximal lesions), 27% fewer cancers
–for death from colorectal cancers: 41% fewer with screening sigmoidoscopy and 68% fewer with colonosc
–reduced mortality from proximal cancers by 53% with colonoscopy and no difference with sigmoidoscopy
–(not surprisingly) those with cancer diagnosed within 5 years of colonoscopy had more aggressive cancers (CpG island methylator phenotype — CIMP — and microsatellite instability)
–benefit of colonoscopy extended 15 years for both proximal and distal tumors. the numbers of individuals are significantly smaller in the group getting screening in the 10-15 year range (and it appears that they do even better), though the group with screening >15 years was worse (but still 31% lower than the controls) — so these authors suggest sticking with 10 years as the appropriate screening interval in those with normal initial colonoscopy.
–also, aspirin had no benefit beyond colonoscopy alone
so, this study did show significant benefit of colonoscopy for proximal tumors (there were articles a couple of years ago suggesting that we only do sigmoidoscopy because it is safer/cheaper/easier on the patient and the data on efficacy for proximal tumors was pretty questionable) and a clear/persistent benefit to screening, even if not repeated for more than 15 years
2. 30 year followup of the minnesota colon cancer control study (see DOI: 10.1056/NEJMoa1300720). 47K people studied, randomized to usual care vs annual or biennial fecal occult blood testing (this was a pretty profound study at the time, though 82.5% of the FOBT slides were rehydrated, which creates 4 times as many false positive results — 9.8% per screening in those with rehydrated slides vs 2.4% in those without rehydration — and then leading to 38% of those in the annual and 28% in those in the biennial groups getting colonoscopy (12,246 colonoscopies!!!). in some ways, this perhaps ended up being more of a colonoscopy study, since so many were done…..). the initial study results reported in 1993 (see Mandel J, NEJM 1993; 328: 1365-71) found a 33% decrease in colorectal cancer mortality, leading to the generalized recommendations to screen for colon ca. results of the longterm followup:
–732 deaths from colorectal cancer (by death certificates)
–screening led to 32% decreased colorectal cancer mortality in the annual screening group and 22% in the biennial group through the 30 years of followup. no diff in all-cause mortality. men benefited more than women in the biennial screening group
–no diff in total mortality
so, pretty clear that colon cancer screening is important, has durable benefit over the longterm, and (i think) both studies ultimately reinforce colonoscopy as the most effective tool.
geoff