The role of cellular mutations was considered in a 2015 study from Johns Hopkins
University. It suggested that the most frequent cause of cancer is not susceptible to
prevention because most cancers occur when DNA is damaged after random errors
or mutations in the replication of DNA that occur when normal cells repeatedly reproduce
as a person ages.
The study found that those tissue types that undergo the
most numerous divisions of cells give rise to human cancers millions of times more
often than other tissue types. According to the study, the lifetime risk of cancers
of many different types is strongly correlated with the total number of divisions
of the normal self-renewing cells that maintain the health of that particular tissue.
And only a third of the variation in cancer risk among tissues is attributable to environmental
factors or inherited predispositions. The majority of cancers are due
to “bad luck,” that is, random mutations arising during DNA replication in normal,
noncancerous stem cells.
Following this publication, a number of scientists have
suggested that the Hopkins study greatly underestimated the role of external risk
factors in the causation of cancer. In addition to random mutations, other factors that affect cancer risk that an individual
cannot control are age, gender, and genetic makeup. It is estimated that 5% to
10% of all cancers are related to specific inherited genes that increase susceptibility
to cancer. In the U.S., one out of eight women (12%) will develop breast cancer,
but women who have inherited one of the BRCA1 and BRCA2 genetic mutations
are about five times more likely to develop breast cancer—approximately 70% by
age 80. Overall, about 5% to 10% of breast cancer cases are thought to be due to
an inherited genetic mutation. Usually, inherited mutations that increase susceptibility
to cancer have incomplete penetrance; this means that not everyone with the
mutation will get cancer.
It may not always be possible to modify or avoid some external environmental factors
that increase the risk of cancer, such as air pollution and workplace exposure
to carcinogens. Bartenders and wait staff may be exposed to secondhand smoke;
workers in chemical plants may be exposed, and workers in the funeral industry
and hair and nail salons may be exposed to formaldehyde and other chemicals.
Although environmental exposures may be important for people living in some
places and working in some occupations, in general, these risk factors are considered
to be responsible for a much smaller portion of cancers than other risk factors
that individuals can control. The ACS estimates that only 6% of all cancer deaths
are the result of exposure to environmental hazards. Other cancer experts have
concluded that this number is underestimated because of widespread occupational
and community exposures to the vast number of untested chemicals Americans now
Studies of risk perception confirm that we tend to worry more about risks over
which we feel we have little control, such as air and water pollution, even if they
do not pose nearly as much of a cancer risk as some other things over which we do
have considerable control, like obesity and consumption of alcohol.19 Unfortunately,
we cannot eliminate all risk of developing cancer, but we can lessen our risk by
getting certain vaccinations, avoiding some environmental exposures, and adopting
the same healthy behaviors on the Lifestyle Checklist that markedly reduce the risk
of cardiovascular and other diseases.
Healthy lifestyle choices include avoiding tobacco, avoiding overweight and obesity,
limiting or better yet avoiding alcohol, engaging in regular physical activity,
protecting skin from the sun, and avoiding or treating certain infections. Eating a
whole-food, plant-based diet abundant in fruits and vegetables and fiber may also
help prevent cancer. Even though recent studies suggest that the proportion of cancers
we can prevent through the adoption of a healthy lifestyle may be lower than
previously thought, reduction of exposure to important behavioral and environmental
risk factors would prevent a substantial proportion of deaths from cancer.
Since it is not possible to prevent all cancers, getting the recommended cancer
screening tests is essential for the early detection of pre-cancerous conditions and
early cancers. Unfortunately, early detection of small cancers does not guarantee
that they have not metastasized and that they are curable, but early detection usually
greatly improves the chances of successful treatment and cure.
This blog presents opinions and ideas and is intended to provide helpful general information. I am not engaged in rendering advice or services to the individual reader. The ideas, procedures and suggestions in that are presented are not in any way a substitute for the advice and care of the reader’s own physician or other medical professional based on the reader’s own individual conditions, symptoms or concerns. If the reader needs personal medical, health, dietary, exercise or other assistance or advice the reader should consult a physician and/or other qualified health professionals. The author specifically disclaims all responsibility for any injury, damage or loss that the reader may incur as a direct or indirect consequence of following any directions or suggestions given in this blog or participating in any programs described in this blog or in the book, The Building Blocks of Health––How to Optimize Your Health with a Lifestyle Checklist (available in print or downloaded at Amazon, Apple, Barnes and Noble and elsewhere). Copyright 2021 by J. Joseph Speidel