INCREASED RISK OF THYROID AND PANCREATIC-CARCINOMA IN FAMILIAL ADENOMATOUS POLYPOSIS

Familial adenomatous polyposis has been associated with several extrai ntestinal cancers, but the relative and absolute risks of these malign ancies have not been determined. Extraintestinal cancers reportedly as sociated with adenomatous polyposis (thyroid gland, adrenal gland, pan creas, and biliary tract) were identified in polyposis patients and th eir at risk relatives in The Johns Hopkins Registry. The incidence rat es of identified tumours were then compared with the general populatio n through person year analysis with adjustment for population. For com parison, the incidence rates of the two most common cancers not associ ated with polyposis (breast cancer in women and lung cancer) were also calculated. There was an increased relative risk of thyroid cancer (r elative risk 7.6; 95% confidence limits (CL) 2.5-17.7) and pancreatic adenocarcinoma (relative risk 4.46; 95% CL 1.2-11.4) in polyposis pati ents and at risk relatives. The absolute risk was 26.8 and 21.4 cases/ 100 000 person years, respectively. No cases of adrenal or biliary can cer were found in this cohort. There was no increased relative risk of lung cancer (95% CL 0.04-1.4) or breast cancer (95% CL 0.04-1.4) over the general population. The relative risks of thyroid and pancreatic cancer are increased in familial adenomatous polyposis, but the absolu te lifetime risk is low. Screening for pancreatic cancer may not be wo rthwhile with currently available methods, but careful physical examin ation of the thyroid gland is warranted along with consideration for u ltrasonography.