Some recent studies have shown that colorectal cancer complicating IBD may not be as common as previously thought or may be decreasing in incidence (Gastroenterology 2012; 143: 375-81 & Gastroenterology 2012; 143: 382-89 ).
The first study used a nationwide cohort of 47,374 Danish patients with IBD over a 30-year period. During a 178 million person-years of follow-up evaluation, 268 patients with ulcerative colitis (UC) and 70 patients with Crohn’s disease (CD) developed colorectal cancer (CRC). The risk was comparable to the general population (RR 1.07)! Furthermore, the relative risk for CRC decreased over sequential time periods: 1.34 (1979-88) to 0.57 (1999-2008).
- UC diagnosed in childhood or adolescence
- longer disease duration
- patients with primary sclerosing cholangitis
Their conclusion, ‘the overall risk of CRC in patients with UC has decreased markedly over time and no longer exceeds that of the general population, at least in the first decade after diagnosis.” And, based on their data, patients with Crohn’s disease are not at increased risk for CRC.
The second study from California used a large Kaiser Permanente database from 1998-June 2010. 29 cancers were identified in CD (n=5603) and 53 in UC (n=10,895) patients. The incidence per 100,000 for CRC was 75 for CD, 76 for UC, and 47 for general population.
These authors conclude that there is an increased risk of CRC in a community-based IBD population between 1998-2010 despite advances in medical treatment.
To understand the discrepancy of these reports, the same issue provides an editorial (page 288). My take is that the current incidence of CRC is lower than in previous reports but that the risk factors identified in the Danish cohort (see above) likely remain important.
- -Gastroenterol 2009; 136: 718. 22% of cancers occurred before recommended surveillance in adults (only 9% if exclusion of patients who had IBD and cancers diagnosed at same time).
- Colon Cancer Survival Calculator http://www.mayoclinic.com/calcs-Gastro 2010; 138: 207-2177 (entire issue)
- -JAMA 2009; 302: 649. Aspirin use likely increases survival after dx of colon cancer. Commentary-Gastro 2010;138: 2012.
- -NEJM 2009; 361: 2449. molecular basis of colorectal cancer
- -Gut 2008; 57: 1246. IBD and colon cancer
- -IBD 2007; 4: 367. 5ASA Rx did not reduce rate of cancer in large study of UC/CD -review of 18,000 colorectal cancer cases. IBD increased risk of CRC 6-7-fold..
- -Clin Gastro & Hep 2006; 4: 1346. aminosalicylates reduce CRC.
- -Gastroenterol 2006; 130: 1030, 1039, 1350. 600 patients followed for 35 yrs: CRC by colitis duration: 2.5% @ 20yrs, 7.6% @ 30yrs, 10.8% @ 40yrs. 5 year survival was 73% among those with cancer. 2nd study showed main CRC risk in UC pts is among those with extensive colitis.
- -Clin Gastro & Hepatol 2004; 2: 1088. Lower cancer risk in this cohort, n=1460. CRC 0.4 @10yrs, 1.1% @ 20yrs, 2.1% @ 30yrs. Lower CRC may be due to more surgery in Rx failures & use of 5-ASA.
- -Clinical perspectives in Gastro 1999; 2: 9 & 25. (review) surveillance/ overview take 4 bx q10cm. start p 8yrs in pancolitis & 15yrs for left-sided dz. Cancer risk: ~5% at 20yrs + 1%/yr p 20yrs in pancolitis.
- -Gastroenterol 2003; 125: 1311. Advancement of dysplasia to cancer in UC.