Increased colorectal cancer risk in first-degree relatives of patients with hyperplastic polyposis syndrome

Hyperplastic polyposis syndrome (HPS) is characterised by the presence of multiple colorectal hyperplastic polyps and is associated with an increased colorectal cancer (CRC) risk. For first-degree relatives of HPS patients (FDRs) this has not been adequately quantified. Reliable evidence concerning the magnitude of a possible excess risk is necessary to determine whether preventive measures, like screening colonoscopies, in FDRs are justified.

We analysed the incidence rate of CRC in FDRs and compared this with the general population through person-year analysis after adjustment for demographic characteristics. Population-based incidence data from the Eindhoven Cancer Registry during the period 1970-2006 were used to compare observed numbers of CRC cases in FDRs with expected numbers based on the incidence in the general population.

A total of 347 FDRs (41% male) from 57 pedigrees were included, contributing 11 053 person-years of follow-up. During the study period, a total of 27 CRC cases occurred among FDRs compared to five expected CRC cases (p<0.001). The RR of CRC in FDRs compared to the general population was 5.4 (95% CI 3.7 to 7.8). Four FDRs satisfied the criteria for HPS. Based on the estimated HPS prevalence of 1:3000 in the general population the projected RR of HPS in FDRs was 39 (95% CI 13 to 121).

FDRs of HPS patients have an increased risk for both CRC and HPS compared to the general population. Hence, as long as no genetic substrate has been identified, screening colonoscopies for FDRs seem justified but this needs to be prospectively evaluated.