Juvenile polyposis syndrome: a study of genotype, phenotype, and long-term outcome.

BACKGROUND: Juvenile polyposis syndrome is phentoypically and genotypically heterogeneous. It is associated with an increased risk of GI cancers, and surveillance is recommended. Few data exist that detail the outcomes of surveillance in juvenile polyposis syndrome. OBJECTIVE: The aim of this study was to review clinical features, genetic mutations, and long-term outcome data in patients with juvenile polyposis syndrome. DESIGN: This study is a retrospective review. SETTING: The Polyposis Registry, St Mark's Hospital, was used in the performance of this study. PATIENTS: Patients with juvenile polyposis syndrome who were followed up at our institution were included. RESULTS: Forty-four patients (27 male) from 30 kindreds were included. Fifteen were diagnosed by screening, and 29 presented symptomatically. Nineteen patients had SMAD4 mutation and 9 had BMPR1A mutation. Five patients (11%) had valvular heart disease. Telangiectasia/vascular abnormalities were observed in 4 (9%) patients, and macrocephaly was observed in 5 (11%). Six patients (14%) developed cancer; 4 had cancer at the time of diagnosis of juvenile polyposis syndrome, 3 developed cancer while on surveillance (1 patient had a second primary). All patients with advanced upper GI disease had SMAD4 mutations. Where germline mutation was known, all patients with telangiectasia had SMAD4 mutation. Seven patients required GI surgery at our institution: colectomy and ileorectal anastomosis (1), restorative proctocolecotomy (1), anteroposterior excision for rectal cancer (1), gastrectomy (2), and laparotomy and intraoperative enteroscopy (1). There were no complications of endoscopic surveillance. Colonic polyps predominated; 535 of 767 (69.8%) of colonic polyps were right sided. One patient had a solitary significant small-bowel polyp. Sixty-five juvenile polyps contained dysplasia (mild to moderate). Two patients had severe dysplasia or cancer found in carpeting polyps. LIMITATIONS: This is a retrospective review. The cohort size, although modest, is good for such a rare condition. CONCLUSION: Extraintestinal features are common. Gastrointestinal surveillance is safe. Most colonic polyps are right sided, and detecting dysplasia is uncommon. Carpeting polyps are of particular concern.

Mucosectomy with handsewn anastomosis reduces the risk of adenoma formation in the anorectal segment after restorative proctocolectomy for familial adenomatous polyposis.

OBJECTIVE: The study compared the risk of adenoma or carcinoma formation in the anorectal segment after either mucosectomy with manual anastomosis or stapled ileoanal anastomosis (IAA) following restorative proctocolectomy (RPC) for familial adenomatous polyposis (FAP). BACKGROUND: Few data exist on the risk of adenoma formation after either technique in FAP. METHODS: All endoscopy and histology reports for patients having RPC for FAP attending for annual pouchoscopy from 1978 to 2007 were reviewed. The incidence, timing, and histological characteristics of adenoma or carcinoma formation were recorded. RESULTS: Of the 206 patients, 140 attended for endoscopic follow-up for a median of 10.3 years after RPC. Fifty-two patients developed neoplastic transformation in the anorectal segment, with a cumulative risk at 10 years of 22.6% after mucosectomy with manual anastomosis and 51.1% after stapled IAA (P < 0.001). The median time to first adenoma was longer after mucosectomy with handsewn anastomosis than after stapled IAA (10.1 vs 6.5 years, P < 0.001). On multivariate analysis, stapled IAA (hazard ratio= 3.45, 95% confidence interval = 1.01­4.98) and age at RPC older than 40 years (hazard ratio = 2.20, 95% confidence interval = 1.01­4.89) were significantly associated with increased risk of adenoma formation. Nine patients developed a large (>10 mm) adenoma. One patient (handsewn ileoanal anastomosis) developed adenocarcinoma in the anorectal mucosa at 13 years and required pouch excision. CONCLUSIONS: Adenoma formation in the anorectal mucosa after RPC for FAP is common but carcinoma is rare. The risk is lower after mucosectomy with handsewn anastomosis than after stapled IAA. Regular endoscopic surveillance after either technique is mandatory.

Features of duodenal cancer in patients with familial adenomatous polyposis.

BACKGROUND & AIMS: Most patients with familial adenomatous polyposis (FAP) develop duodenal adenomas; duodenal cancer is a major cause of mortality in this patient group. We reviewed cases of duodenal cancer in patients with FAP to identify factors that determine long-term cancer risk. METHODS: Twenty FAP patients (12 male) were identified from a registry database search. Data from registry and medical notes and endoscopic and histopathologic reports were evaluated. RESULTS: Of the cancers that developed in these patients, 11 were ampullary and 9 were duodenal. The median age at cancer diagnosis was 53 years. Seventeen patients died (median age at death, 57 y; median survival from diagnosis, 11 mo); the cause of death was metastatic or duodenal/ampullary cancer in 14 patients. Fifteen patients presented symptomatically (including 3 interval cancers while on surveillance). Two were diagnosed at surveillance and 3 were diagnosed during surgery performed for endoscopic features of advanced benign disease. Duodenal cancers were associated with a significantly lower mean colonic polyp count than ampullary cancers (496 +/- 282 vs 1322 +/- 735; P = .025); there appeared to be familial clustering of this cancer. When endoscopic data were available (n = 11 of 20), all ampullary cancers arose from ampullas greater than 1 cm. The Spigelman stage did not predict risk of ampullary cancer but did predict duodenal cancer (median stage 2 vs stage 4 for duodenal cancer). CONCLUSIONS: Once cancer arises in patients with FAP, prognosis is poor, so cancer prevention should be the main goal. Surveillance intervals should reflect both Spigelman staging and ampullary disease.

Promoter hypermethylation leads to decreased APC mRNA expression in familial polyposis and sporadic colorectal tumours, but does not substitute for truncating mutations.

Germline mutations in the tumour suppressor APC cause familial adenomatous polyposis (FAP), and somatic mutations are common in sporadic colorectal cancers (CRCs). Hypermethylation of APC promoter 1A has been reported in a substantial proportion of sporadic CRCs and may cause transcriptional silencing. Methylation has been proposed as an alternative to mutation or loss of heterozygosity as a mechanism of gene inactivation. However, the significance of APC methylation has remained unclear, because it has not previously been related to the presence of mono- or bi-allelic mutations at APC. We examined 103 FAP adenomas, 11 attenuated FAP adenomas, 31 sporadic CRCs and 30 CRC cell lines, all with known germline and/or somatic APC mutations. Overall, APC promoter 1A methylation was detected in 27-45% of colorectal tumours and cell lines, but generally not in histologically normal colorectum. In contrast to previous reports, methylation was detected in similar proportions of FAP/AFAP and sporadic CRCs. Importantly, methylation was independent of the presence, number and positions of APC mutations and was not associated with the CpG island methylator phenotype. Methylation resulted in a decrease or loss of 1A isoform mRNA and reduced total APC transcript levels, although expression was retained from promoter 1B. However, neither APC protein levels, nor transcription of a panel of Wnt target genes was associated with methylation status. Our data suggest that APC promoter 1A hypermethylation may influence APC expression levels in a subtle fashion, but methylation does not result in complete gene inactivation or act as a 'second hit'.

Refining the relation between 'first hits' and 'second hits' at the APC locus: the 'loose fit' model and evidence for differences in somatic mutation spectra among patients.

The site of the 'first hit' in the APC tumour suppressor gene determines the type of the 'second hit', both in familial adenomatous polyposis (FAP) and sporadic colorectal tumours. Mutations near codon 1300 are associated with loss of heterozygosity (LOH) of the wild-type allele; other tumours tend to have two protein-truncating mutations. In this study, we have confirmed and refined the LOH-associated region in colorectal FAP: allelic loss in adenomatous polyps tended to occur when the germline mutation lay in the region of the APC gene between the first and second beta-catenin degradation repeats (codons 1285-1378). LOH generally occurred by mitotic recombination, leaving two identical alleles, each encoding a protein with one remaining beta-catenin degradation repeat. For patients with germline mutations that truncated the protein before the first repeat (codon 1264), LOH was very rare and tumours generally acquired a somatic mutation which left two, or less often one, repeats remaining in the protein. In our sample set, patients with germline mutations after the second beta-catenin degradation repeat tended to have undetectable, presumably cryptic, somatic mutations in their polyps. Exceptions to these rules were, however, not uncommon. Although the site of the germline mutation was the strongest determinant of the somatic mutation in FAP tumours and most patients showed no clear tendency to acquire specific types of truncating 'second hit', a minority of patients did have unusual somatic mutation spectra in their polyps. Thus, some individuals may be predisposed to particular types of 'second hit' (for example, frameshift rather than nonsense changes). Overall, disease severity (polyp number) did not vary with individuals' spectrum of somatic APC mutations, providing no clear evidence for modifier genes that influence disease severity in this fashion. Our data are consistent with the hypothesis that there exists an optimal level of beta-catenin signalling in colorectal tumours and that the APC mutation spectrum principally reflects this fact. The association between 'first hits' and 'second hits' at APC is not, however, so strong as to suggest that tumorigenesis only occurs if the genotype is optimum; we suggest 'relaxed' terminology, the 'loose fit' model, to describe this situation.