Family History of Colorectal Polyps Increase the Risk of Colorectal Cancer: Study

Existing data on the association between family history of colorectal polyps and CRC risk are inconclusive. Whereas some studies reported an increased risk of CRC in first degree relatives of patients with a history of colorectal polyps, others indicated that the risk varied by polyp type and was restricted to large or advanced adenomas. Therefore, Prof.Mingyang Song and his team conducted a study to assess the risk of colorectal cancer (CRC) in first degree relatives (parents and full siblings) of patients with precursor lesions (polyps) for CRC.

In a nationwide case-control study, the researchers used information from several national registers. The researchers included a total of 68 060 patients with CRC from the nationwide ESPRESSO (Epidemiology Strengthened by histoPathology Reports in Sweden) cohort, which included information on gastrointestinal biopsy samples from all 28 pathology departments in Sweden between 1965 and 2017. They further matched the patients with 333 753 controls. The primary outcome assessed was multivariable-adjusted odds ratios of CRC according to the number of first degree relatives with a colorectal polyp and the histology of polyps and age at diagnosis in first degree relatives. The researchers also performed subgroup analysis, according to age at CRC diagnosis and evaluated the joint association of family history of colorectal polyps and family history of CRC.

Key findings of the study were:

• After adjusting for family history of CRC and other covariates, the researchers noted that having a first degree relative with a colorectal polyp (8.4% (5742/68 060) in cases and 5.7% (18 860/333 753) in controls) was associated with a higher risk of CRC (odds ratio 1.40).
• They observed that the odds ratios ranged from 1.23 for those with hyperplastic polyps to 1.44 for those with tubulovillous adenomas.
• They noted that the association between family history of polyps and CRC risk was strengthened by the increasing number of first degree relatives with polyps (≥2 first degree relatives: 1.70) and decreasing age at polyp diagnosis (<50 years: 1.77).
• They found a strong association for early-onset CRC diagnosed before age 50 years (≥2 first degree relatives: 3.34 for heterogeneity by age of CRC diagnosis).
• In the joint analysis, they noted that the odds ratio of CRC for individuals:

◊ With two or more first degree relatives with polyps but no CRC was 1.79 (1.52 to 2.10),

◊ With one first degree relative with CRC but no polyps was 1.70 (1.65 to 1.76), and

◊ With two or more first degree relatives with both polyps and CRC was 5.00.

The authors concluded, "After adjusting for family history of CRC, the siblings and children of patients with colorectal polyps are still at higher risk of CRC, particularly early onset CRC. Early screening for CRC might be considered for first degree relatives of patients with polyps."

For further information:

https://www.bmj.com/content/373/bmj.n877