CANCER PREVENTION

by drnieman on April 27, 2017

in Monthly

Each year close to 11,000 children between the ages of 0 and 14 years receive a cancer diagnosis in North America. Between 1975 and 1979 the 5-year survival rate was 58%. But due to impressive accomplishments in oncology, the survival rate for patients diagnosed between 2003 and 2009 has climbed to 83%.

Even when the treatment modalities have improved dramatically—especially for childhood leukemia—the Holy Grail remains the prevention of cancer by modifying the environment and encouraging healthy lifestyle. Is it a realistic goal? Is there any hope of prevention, or do we have to settle for the compromise of only modifying some risk factors rather than preventing cancer? Is it possible to start in early childhood, when there may narrow window of opportunity and thus impact the future?

Organizations such as the WHO and the CDC have invested millions of dollars to study this topic. The Healthy People 2020 goal for cancer is to reduce the number of new cancer cases.
Incidence rates have increased over the past decade for certain types of childhood cancers such as leukemia and renal carcinomas. In adults there is an increase in melanomas, myeloma, leukemia, cancers of the pancreas, liver, thyroid and kidney.

A recent publication in a Supplement to Pediatrics (Nov 2016) written by the Cancer Prevention Across the Lifespan workgroup indicates that overall we are getting closer to the goal of primary prevention, but because the causes of cancer and the various associations with exposures to pesticides, chemicals, alcohol are so complex, multifactorial and multigenerational, it may take much more funding for research before we can truly hope to prevent cancer by starting in early childhood—and even in utero.
We know that when weight gain during pregnancy is too rapid or too slow that it may put the fetus at risk for obesity at a later age. This in turn is a risk factor for the development of some cancers, especially breast cancer.

The pregnant mother’s use of alcohol, and tobacco and chemical exposures at work or where pesticides are used also increase the risk of cancer. Other factors which play important roles is the duration of breastfeeding, the prenatal consumption of folic acid, day care attendance and adverse childhood experiences which so often are linked with the stressors of poverty and a lower socioeconomic status. Studies of childhood brain tumors reported associations with benzene exposure via tobacco smoke, fuel evaporation and industrial sources (Benzene tends to bind strongly to the brain and fatty tissues and can cross the placenta)

Disparities in the delivery of healthcare in early life and the associated toxic stress or adverse childhood events (maltreatment and abuse) are seen as risk factors for the development of cancer.
Leukemia is still the most common cancer in children. Today close to 90% of children are cured of this once nearly uniformly fatal disease. Exposures to solvents, traffic fumes, pesticides and tobacco smoke have consistently demonstrated positive associations with the risk of developing childhood leukemia. Pooled data from the Childhood Leukemia International Consortium, including 13 studies worldwide and representing 10,000 leukemia cases reported elevated risks of leukemia with the home use of pesticides before and after birth. Maternal occupational exposure to pesticides also increased the risk.

In a recent survey of pediatric oncologists and nurse practitioners 61% of the respondents believed that environmental chemicals are important contributors to childhood cancer and 88% reported receiving questions from families about environmental exposures. But even so 44% felt uncomfortable talking to with their patients about environmental links and 92% said they would like to have more information on this topic.

A Cancer Panel convened by the US President summarized its assessment of the impact of environmental causes of cancer by concluding “The true burden of environmentally induced cancers has been grossly underestimated.” The WHO has reached a similar conclusion and called for action to address this problem.
Environmental organizations have assembled online resources which provide information about chemicals commonly found in the workplace and at home. (See www.chemhat.org) The University of California at Berkeley also has a similar web site (www.goodguidw.com/)

Can adolescent girls who grow up in breast cancer families modify their risk for cancer? When a woman at the highest risk for breast cancer due to mutations in the BRCA1 and BRCA 2 carrier genes encouraged their daughters to engage in more physical activity and avoid alcohol and tobacco smoke there appears to be a delay in onset of cancer. This opens the conversation of epigenetics, and the science of environmental changes impacting the expression of genes.

The founding director of Yale University’s Prevention Research Center, Dr. David Katz, published a book Disease Proof on this topic and claims that changes in lifestyle can indeed reduce the risks of cancer.
Earlier this year a comprehensive, quantitative Alberta-based study led by Dr. Christine Friedenreich showed that 45% of cancers in Alberta can be prevented by reducing risk factors related to lifestyle. All researchers are quick to point out that the causes of cancer are complex and the primary prevention at this time may in fact be a dream until we get more clarity on issues such as the timing and duration of exposures to chemicals and the role of nutrition, exercise, stress and mental health.

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