Risk of cancer in ulcerative colitis

Precancer in ulcerative colitis: the role of the field effect and its clinical implications

Cumulative evidence indicates that a significant proportion of cancer evolution may occur before the development of histological abnormalities. While recent improvements in DNA sequencing technology have begun to reveal the presence of these early preneoplastic clones, the concept of 'premalignant field' was already introduced by Slaughter more than half a century ago. Also referred to as 'field effect', 'field defect' or 'field cancerization', these terms describe the phenomenon by which molecular alterations develop in normal-appearing tissue and expand to form premalignant patches with the potential to progress to dysplasia and cancer. Field effects have been well-characterized in ulcerative colitis, an inflammatory bowel disease that increases the risk of colorectal cancer. The study of the molecular alterations that define these fields is informative of mechanisms of tumor initiation and progression and has provided potential targets for early cancer detection. Herein, we summarize the current knowledge about the molecular alterations that comprise the field effect in ulcerative colitis and the clinical utility of these fields for cancer screening and prevention.

Analysis of mutations in TP53, APC, K-ras, and DCC genes in the non-dysplastic mucosa of patients with inflammatory bowel disease

BACKGROUND AND AIMS

Patients with ulcerative colitis (UC) and Crohn's disease (CD) have a high risk for colorectal cancer (CRC). To understand the molecular basis of colitis-associated CRC, we analyzed alterations in TP53, APC, K-ras, and DCC genes in the non-dysplastic UC and CD colon.

MATERIALS AND METHODS

Endoscopic biopsies were collected from six predefined colon sites of 35 UC and 12 CD patients for DNA extraction and genetic analysis.

RESULTS

A mutation was found in codon 1141 of the APC gene of two CD patients, being somatic in one and germinative in the other. The mutation seen in both patients was a base exchange of thymine for cytosine, resulting in an exchange of leucine for serine. We did not detect any mutations in the other samples analyzed.

CONCLUSIONS

Mutations in APC gene may occur in the non-dysplastic CD mucosa of patients with disease for more than 10 years. The follow-up of these patients will show the likelihood of mutant APC progressing to CRC in CD. Further analysis will be required for evaluating the impact of these findings in the context of cancer surveillance in inflammatory bowel disease.

Incidence and management of colorectal cancer in liver transplant recipients

Liver transplant recipients are at an increased risk of developing de novo malignancies because of the prolonged immunosuppression necessary to avoid acute and chronic rejections. Skin cancers and lymphoproliferative diseases are the most common malignancies, but the overall incidence of colon cancer in this patient population does differ from that of the general population. Therefore, colorectal cancer (CRC) is a major health concern in liver transplant recipients. Furthermore, there are unique subsets of liver transplant recipients, such as those with primary sclerosing cholangitis and inflammatory bowel disease, who are at an increased risk for developing CRC after liver transplantation and might require special screening/surveillance strategies. The similar principles for management of colon cancer can be applied to transplant recipients if the adjustment to maintain the need for the long-term immunosuppression is made. Colectomy can be performed safely during the posttransplantation period. Prophylactic colectomy at the time of liver transplantation has been performed in some patients at high risk or with known premalignant conditions. Chemotherapy with 5- fluorouracil and oxaliplatin has been used in transplant recipients for the treatment of metastatic CRC; however, further research is required to examine the safety, tolerability, and efficacy of combination chemotherapy and biologic agents in this patient population. This review summarizes the incidence, risk factors, diagnosis, and management of de novo CRC in liver transplant recipients.

Colorectal cancer after orthotopic liver transplantation

There is an increased incidence of de novo malignancies in post-liver transplant patients, commonly associated with chronic viral infection comprising lymphoproliferative disease and skin cancers, including squamous cell carcinoma and Kaposi's sarcoma. The overall incidence of colorectal cancer however in this population seems to be no different to the age and sex matched general population. In identified high risk patients like those with primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD), the incidence of colorectal cancer appears to be higher. In IBD, like other pre-malignant conditions, the risk of developing malignancy increases exponentially with time, raising the question of whether the apparent increase in the incidence of colorectal cancer is the result of liver transplantation and immunosuppression or due to the natural history of IBD. For these PSC recipients, pre-transplant screening with colonoscopy and post-transplant surveillance for malignant change in the large bowel is crucial. The behaviour of inflammatory bowel disease post-liver transplant is largely unpredictable despite immunosuppression. Colorectal cancer when it occurs in the post-liver transplant patient should be managed according to current guidelines, stage for stage as for the population in general coupled with reduction in immunosuppression treatment.

Colorectal cancer in patients with inflammatory bowel disease after liver transplantation for primary sclerosing cholangitis

BACKGROUND

Patients with primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD) may have an increased risk of developing colorectal cancer (CRC) after liver transplantation (LT). We evaluated our patients with PSC after LT to identify risk factors for CRC and its impact on survival.

PATIENTS AND METHODS

A total of 152 patients (108 men, 100 with IBD) with PSC who underwent 173 LTs between 1986 and May 2000 were analyzed in three groups: (1) PSC without IBD (n=52); (2) PSC with colectomy (pre-LT and at LT) (n=17, colectomy pre-LT in 13 and simultaneous colectomy at LT in four); and (3) PSC with IBD and an intact colon (n=83). The following factors were studied: age, gender, liver, and renal biochemistry, international normalized ratio, Child-Pugh stage, operative time, blood use, hospital stay, immunosuppression, risk of CRC, retransplantation rate, and mortality.

RESULTS

The incidence of CRC after LT was 5.3% (8/152) compared with 0.6% (7/1,184) in non-PSC cases (P<0.001). All CRCs in the PSC group were in patients with IBD and an intact colon. The cumulative risk of developing CRC in the 83 patients with an intact colon and IBD was 14% and 17% after 5 and 10 years, respectively (PSC non-IBD group 0% risk after 10 years, P<0.06). The multivariate analysis showed three significant variables related to the risk of developing CRC: colonic dysplasia after LT (P<0.0003), duration of colitis more than 10 years (P<0.002), and pancolitis (P<0.004). The cause of death in patients with CRC was cancer related in 75% of cases with a reduced 5-year survival of 55% versus 75% without CRC (not significant).

CONCLUSION

Patients with PSC undergoing LT with a long history of ulcerative colitis and pancolitis have an increased risk of developing CRC with reduced survival. We advocate long-term aggressive colonic surveillance and colectomy in selected high-risk patients with longstanding severe colitis.

Colon cancer: detection and prevention

Recent data have advanced our ability to detect, survey, and manage patients with colonic neoplasia. Current studies and consensus statements increasingly support the role of colonoscopic screening over less invasive testing such as FOBT or FS for appropriately selected individuals. There are many issues, however, that remain unresolved. What is the appropriate surveillance of an individual with a single family member who had colon cancer at an early age? How should family members of suspected HNPCC kindreds be managed? There has yet to be a prospective cohort validation of the Bethesda criteria in directing clinical practice, with the endpoint of mortality reduction. Questions regarding prophylaxis with dietary supplements and medications are exciting areas that are currently under study. As newer technologies become clinically available for molecular diagnostics and screening, and virtual colonoscopy with computed tomography and magnetic resonance disseminates, there will undoubtedly be new questions to be answered regarding their ability to aid in the detection and management of colon cancer.

In vivo detection of experimental ulcerative colitis in rats using fiberoptic confocal imaging (FOCI)

Fiberoptic confocal imaging (FOCI) is a noninvasive microscopic technique that enables subsurface imaging of living tissue in vivo. The aim of the present study was to assess the suitability of FOCI for the in vivo detection of early subsurface changes in the mucosal architecture of the colon in a rat model of ulcerative colitis. Mild colitis was induced in Sprague-Dawley rats (180-250 g) by the oral ingestion of 5% (w/v) dextran sulfate sodium (DSS; Mr 40,000 Da) in drinking water. Control animals were provided with water ad libitum. After three, five or seven days of oral consumption of DSS, the mucosal surface of the colon of anesthetised rats was surgically exposed. Morphological changes in the mucosa were examined (Optiscan F900e personal confocal system with rigid endomicroscope attachment; excitation 488 nm argon ion laser, detection above 515 nm) following the topical application of a fluorescent dye (fluorescein, eosin, or acridine orange). Confocal images were correlated with conventional histology and clinical parameters including occult blood and stool consistency. Histological evaluation of colon sections demonstrated that DSS-induced colitis was characterized by focal loss of mucous crypts, loss of epithelial cells, and neutrophilic infiltration into the mucosa. The extent of mucosal damage was positively correlated with the time of ingestion of DSS. Morphological changes associated with disease activity could be detected microscopically in vivo using FOCI but were not evident by visual inspection of the colon surface. Acridine orange enabled imaging of the colonic crypts at the surface of the mucosa. Morphological changes associated with colitis, including inflammatory cell infiltrate, crypt loss, and crypt distortion, could be detected using this fluorophore. Application of fluorescein and eosin enabled subsurface imaging of the lamina propria surrounding the crypts; however, no change in structure was detected in association with colitic disease activity. This study has shown that the topical application of acridine orange enables in vivo imaging of early colitis in a rat model. FOCI may be suitable for the diagnosis and monitoring of human inflammatory bowel disease.