Although early onset cancers tend to have a more pronounced hereditary component than cancers that develop at a later age, there is still an increased risk of some familial cancers even when a parent is diagnosed at an older age, according to the results of a study published in the British Medical Journal.
The chance of an individual developing cancer depends on both genetic and non-genetic factors. A genetic factor is an inherited, unchangeable trait, while a non-genetic factor is a variable in a person’s environment, which can often be changed. A genetic predisposition means that a person may be at higher risk for a certain cancer if a family member has that type of cancer. Of course, a family history of cancer is not a modifiable risk factor—however, researchers continue to explore the risks and develop a better understanding of familial risk in order to improve screening and prevention for the disease.
Researchers used the nationwide Swedish Family-Cancer Database in order to examine the familial risk of concordant cancer (meaning parent and offspring have the same type of cancer) for offspring as a function of the age at which a parent was diagnosed. The study population included more than 12.2 million people born after 1931. Since they were examining familial risk in advanced age, researchers limited their results to cancers with at least 50 cases in the offspring of parents whose cancer was diagnosed at age 80 or older.
They found that the highest familial risk occurred in people who were diagnosed at an early age and whose parents were diagnosed with the same type of cancer at an early age; however, an increased risk still exist for several cancers when diagnosed at advanced ages.
In fact, for some types of cancer, the excess risk that results from family history included cancers diagnosed in parents even at ages 90 and older—including skin cancer (90 percent excess risk), colorectal cancer (60 percent), breast cancer (30 percent), and prostate (30 percent).
One example—when a parent’s colorectal cancer was diagnosed before age 40 and the offspring was diagnosed before age 60, the hazard ratio was 9.9. When the parent was diagnosed between ages 80-90, the hazard ratio declined to 1.7, but remained significant.
The researchers concluded that the highest familial risks of cancer are observed in offspring whose parents received a diagnosis of a concordant cancer at an earlier age, but increased risks exist even in several cancers of advanced ages. They suggest that increased clinical surveillance is important even in families where parents are diagnosed at a late age.
Kharazmi E, Fallah M, Sundquist K, et al. Familial risk of early and late onset cancer: nationwide prospective cohort study. British Medical Journal. 2012;345:e8076.