Cancer etiology - genetic or environmental?

Etiology is the study of causation. When we consider the etiology of cancer - is it caused by genetic or environmental factors? In order to prevent what is going to kill you, you need to know what those fctors are.

Let's zero in on Canada's number one killer: cancer. When you search Canadian vital statistics, consider the latest figures which I reviewed, those for the year 2011, there were 246,596 deaths from cancer. Statistics Canada divided the population into 4 age groups and calculated the percentage of cancer deaths: 

• Ages 1-24 > 10% deaths from cancer 
• Ages 25-44 > 21% deaths from cancer 
• Ages 45-64 > 44% deaths from cancer 
• Age 65 and older > 28% deaths from cancer

Not surprising, cancer was the number one cause of death for Canadians in all 4 age groups. What did surprise me was that cancer caused 10% of the 2679 deaths in the youngest age group. Most oncologists estimate that only 10-20% of cancers are genetically determined, with the rest due to environmental factors, with diet responsible for 35%, tobacco 25% (for males, with the percentage for females rapidly approaching the same figure). 

It is also well documented that the main reason for the higher cancer deaths in those 45 and over for lung cancer and possibly also for the other environmental factors like diet and radiation is due to the so-called lag period. 

If this hypothesis for the mechanism of environmental carcinogenesis applies, then genetically determined cancers in the 1-24 age group should be responsible for more cancer deaths, with fewer from environmental factors such as food, smoking, radiation, etc. Such information may give the oncologists and genetic counselling specialists new tools for their management of this major killer.

first posted: September 20, 2016 by Dr. Semeon B. Hrushovetz - edited September 3, 2023