One-third of all cancers maybe inherited

Muci et al published in JAMA the results of a trial that suggests that approximately one-third of all cancers are due to inherited genes. 

The investigators looked at data from 80 309 monozygotic and 123 382 same-sex dizygotic twin individuals (N = 203 691) within the population-based registers of Denmark, Finland, Norway, and Sweden, who were part of the Nordic Twin Study of Cancer. 

Twins were followed up a median of 32 years between 1943 and 2010. There were 50 990 individuals who died of any cause, and 3804 who emigrated and were lost to follow-up.

The main outcome was incident cancer and time-to-event analyses were used to estimate familial risk.

A total of 27 156 incident cancers were diagnosed in 23 980 individuals, translating to a cumulative incidence of 32%. Cancer was diagnosed in both twins among 1383 monozygotic (2766 individuals) and 1933 dizygotic (2866 individuals) pairs. Of these, 38% of monozygotic and 26% of dizygotic pairs were diagnosed with the same cancer type.

The analysis of data found that overall heritability for cancer was 33 percent among the entire study population, and significantly higher for certain types of cancers.  Significant heritability was found in 58 percent of diagnosed skin melanomas, 57 percent of prostate cancers, 43 percent of non-melanoma skin cancers, 39 percent of ovarian cancers, 38 percent of kidney cancers, 31 percent of breast cancers and 27 percent of uterine cancers.  In the same study researchers identified a set of cancers in which genetics play a very small role. This group includes lung cancer (18 percent), colon cancer (15 percent), rectal cancer (14 percent), and head and neck cancer (9 percent).”

In this long-term follow-up study among Nordic twins, there was significant familial risk for cancer overall and for specific types of cancer.  This information about hereditary risks of cancers may be helpful in patient education and cancer risk counseling.

One in Two Americans will develop Cancer in their Lifetime

According to the American Cancer Society the lifetime risk of developing or dying from cancer refers to the chance a person has, over the course of his lifetime, of being diagnosed with or dying from disease. These risk estimates, like annual incidence and mortality data, provide another measure of how widespread cancer is in the United States.

The information is from the US National Cancer Institute’s Surveillance Epidemiology and End Results (SEER) Database, and is based on incidence and mortality data for the United States from 2009 through 2011.

The risk is expressed both in terms of a percentage and as odds. For example, the risk that a man will develop bladder cancer during his lifetime is 3.83%. This means he has about 1 chance in 26 of developing bladder cancer (100/3.83 = 26.1). Put another way, 1 out of every 26 men in the United States will develop bladder cancer during his lifetime.

The risk for women of developing cancer at any site is 37.8% while their risk of dying due to cancer is 19.6%.  This means 1 in 3 women will develop cancer in their life while 1 in 5 will die from the disease.

The risk for females for developing breast cancer, the most common cancer in women, is 12.3%.   This means 1 in 8 women will develop the disease while the risk of dying form cancer is 2.7%, which means 1 in 37 will die from the disease.

The risk for men of developing cancer at any site is 43.3% while the risk of dying due to cancer is 22.6%.  This means 1 in 2 men will develop cancer in their life while 1 in 4 will die from the disease.

The risk for men to develop prostate cancer, the most common cancer in men, is 15%.   This means 1 in 7 men will develop the disease while the risk of dying is 2.6%, which means 1 in 38 will die from the disease.

According to a study published in the British Journal of Cancer, the odds of developing cancer over the course of one’s life in the UK has increased from 38.5% for men born in 1930 to 53.5% for men born in 1960. For women it increased from 36.7 to 47.5%.

Therefore according to the data for the United States and United Kingdom over half of people who are currently adults under the age of 65 years will be diagnosed with cancer at some point in their lifetime.