Relatives of patients with colorectal cancer (CRC) benefit from earlier CRC screening. Exact risk-adapted starting ages for CRC could be used to better counsel individuals about the appropriate age to be screened, according to study data published in Gastroenterology.
Investigators abstracted data from nationwide family-cancer datasets in Sweden. Family data from the Multi-generation Register were linked to information from national censuses, death notifications, and the Swedish Cancer Registry. Swedish residents with information available in these datasets from the years 1958 to 2015 were eligible for inclusion. Follow-up began in 1958, at birth, or upon immigration; follow-up concluded with CRC diagnosis, emigration, death, or at the end of 2015.
The primary outcome measure of the study was CRC diagnosis, identified from codes in the Swedish Cancer Registry. The primary exposure was family history of CRC. Family history was treated as a time-varying exposure and was updated if the CRC status of first- and second-degree relatives changed during follow-up. The 10-year cumulative risk of CRC by age was calculated for each strata of family history: no family history of CRC; 1 first-degree relative with CRC; 1 first-degree relative and 1 second-degree relative with CRC; and so on. From the cumulative risk scores of cohort members, risk-adapted recommendations for screening ages were calculated and compared to the current recommended age (50 years).
The study cohort comprised 12,829,251 individuals with genealogical information, of whom 51% were men (N=6,527,022). Median per-person follow-up time was 35 years. During the total study period, 173,796 (1.35%) individuals developed CRC. Of patients without family history, the cumulative CRC risk at age 50 was 0.44%. Of patients with 1 affected first-degree relative, the 0.44% risk level was attained 5 years earlier, at age 45 years. The risk-adjusted screening age continued to decrease as the number of affected relatives increased. Individuals with both an affected first-degree relative and an affected second-degree relative reached the 0.44% risk level at age 34. Patients with 2 or more affected first-degree relatives and any number of affected second-degree relatives reached the same risk level 28 years earlier (age 22). The age of diagnosis of affected relatives also influenced relative risk; individuals with an affected first-degree relative diagnosed before age 45 reached the 0.44% risk threshold at age 34. If a first-degree relative was diagnosed between 45 and 49, patients reached the risk threshold at age 37.
These data provide evidence-based recommendations for earlier CRC screening of individuals with affected relatives. Patients with family history attained cumulative risk for the average-risk population between 3 and 28 years earlier. Per these findings, screening guidelines stratified by family history may be important for earlier detection of CRC in high-risk individuals.
Tian Y, Kharazmi E, Brenner H, et al. Calculating starting age for screening in relatives of patients with colorectal cancer based on data from large nationwide datasets [published online April 3, 2020]. Gastroenterology. doi: 10.1053/j.gastro.2020.03.063