It has long been known that when a parent develops cancer at a relatively young age, the offspring are at significantly increased risk of getting cancer themselves.
What is not clear, however, is whether there’s a family risk – and how great that risk is—if a parent gets cancer much later in life, after they’ve turned 80. One of the reasons for this gap is that there are very few comprehensive databases that researchers can mine for information.
Now, researchers from the German Cancer Research Centre and Lund University in Sweden used the Swedish Family-Cancer Database (the largest one of its kind) of nearly 8 million offspring and their parents to answer these questions.
Parents were born between 1867 and 1993 and offspring were born between 1932 and 2008. The researchers only looked at cancer rates in offspring up to age 76.
The study, published online in the BMJ, found that even when parents developed cancer after 80 years of age, the risk of the same cancer in offspring was significantly higher than those whose parents had not gotten cancer.
Those whose parents were diagnosed at a younger age still had the highest risk of cancer.
But, if parents were affected between the ages of 80 and 89, the offspring had 2.3 times the risk of melanoma, 2 times the risk of squamous cell skin cancer, 1.9 times the risk of prostate cancer, 1.7 times the risk of non-Hodgkin lymphoma and urinary bladder cancer, and 1.6 times the risk of breast cancer and colorectal cancer. Even for those whose parents were diagnosed in their 90s, the risks were still increased, albeit only slightly less than those diagnosed in their 80s.
Overall, having a parent who developed cancer at any age increased risks for each cancer as follows: non-Hodgkin lymphoma, 1.6 percent; urinary bladder, 2.8 percent; melanoma, 4.6 percent; lung, 5 percent; colorectal, 6.4 percent; breast, 8.8 percent and prostate, a huge 30.1 percent.
The researchers also found the majority of cancers occur after the age of 69.
“Familial cancers might not be early onset in those whose family members were affected at older ages,” said Dr. Elham Kharazmi, of the German Cancer Research Center in Heidelberg, Germany, and the study's co-author.
Incidentally, it appears that if a parent develops cancer at a young age, and the child makes it into his or her 60s cancer-free, the child does not carry an increased risk of cancer.
“The higher risk of familial cancer for offspring whose parents were affected at young ages disappeared in this subgroup of offspring,” Kharazmi said. “This suggests that familial cancers are early onset mainly in those individuals whose family members are affected at early ages."
Knowing you’re at increased risk of cancer can allow you to take steps to prevent those cancers, including reducing risk factors such as smoking, being overweight and being sedentary, as well as being more vigilant about early detection screening.