Cancer Prevention Backgrounder: Toward the Future of Cancer Prevention
Can most types of cancers be prevented?
It's a question that has emerged in the past 20 years, given advances in screening and early diagnosis, rapid developments in genetics and molecular biology, and progress in the treatment of early disease and in next-generation targeted therapies. And finding answers is one of the top goals of The University of Texas M. D. Anderson Cancer Center, which has one of the largest cancer prevention research programs in the world.
M. D. Anderson was among the first to begin dedicated prevention research efforts in the late 1970s. A decade ago, nine faculty were working on 23 projects - a pursuit that was regarded as trend-setting at the time. The cancer center's focus on prevention has grown so much in recent years that the 48 faculty, involved in 140-plus research projects and clinical programs valued at more than $20 million in 2005 alone, just moved into the new Cancer Prevention Building.
In addition to housing faculty offices, the building's Cancer Prevention Center and new Behavioral Research and Treatment Center provide advanced early detection and risk-reduction services and state-of-the-art biobehavioral and psychosocial research venues.
These two centers involve only a sliver of the basic and applied research under way. In short, the researchers, physicians, nurses, employees and volunteers that staff this building aim to bring about a future that may some day be free of cancer.
They also are the first to say that attaining this goal will not be easy; that prevention will require developing a wide variety of strategies and associated tactics to curtail the variety of different diseases, all called cancer, that have now emerged as the number one killer of Americans under age 85.
"Prevention is very broad," says Bernard Levin, M.D., vice president and head of the Division of Cancer Prevention and Population Sciences. "It is not just prevention of cancer development, but includes advances in diagnosis and treatment that reduce suffering and mortality from the disease."
In short, "prevention," as oncologists use the term spans the gamut from stopping cancer from ever developing to improving cure rates through earlier detection, thereby preventing recurrence and death. Prevention also encompasses preventing suffering from cancer by controlling pain and meeting psychosocial needs.
"Because we see prevention as so inclusive, the task we have set for ourselves is very difficult and won't likely be accomplished for decades," Levin says. "But if we can lessen the odds that even one person will develop cancer, or suffer or die from it, we have moved one step closer to our goal. It is that march of progress over time that will make a difference in the future."
Developing a model of cancer prevention
Debate exists on how many cancer deaths are preventable in principle - estimates range from 50% to 80% - but most researchers agree that tobacco use (mostly smoking) accounts for the majority. Today, cigarette smoking claims about 438,000 premature deaths in the U.S. annually. It is responsible for up to one-third of all cancer deaths and accounts for 20% of annual U.S. mortality due to all causes, according to the federal Centers for Disease Control and Prevention.
And while lung cancer is tobacco's primary killer, smoking also is responsible for many other types of tumors. Since the same carcinogens that cause lung cancer also affect the lining of the entire respiratory tract and are absorbed by the blood and then excreted as waste, smoking is a major cause in cancers of the oral cavity, pharynx, larynx, esophagus, pancreas, stomach, kidney and bladder, among others. The American Cancer Society states that smoking damages almost every organ in the body.
The cumulative consequence of other lifestyle factors on cancer risk such as obesity, physical activity, diet/nutrition and alcohol use, as well as infectious agents and occupational exposures, is not fully known, although some experts say it may approach that of tobacco use.
Given the certainty that the number one cause of cancer illness and death is also the most preventable, scientists to date have aimed much of cancer prevention science on smoking. "Because tobacco is responsible for an impressive one-third of cancers, prevention efforts naturally begin with it," Levin says. But he and colleagues in the Division of Cancer Prevention and Population Sciences have moved beyond solely delivering advice to stop smoking.
They are developing a comprehensive program that not only devises innovative behavioral and pharmacological approaches to smoking prevention and cessation, but burrows down to the molecular level on every aspect related to prevention.
For example, researchers at M. D. Anderson are looking at brain physiology; variations in genes that "favor" smoking and other addictive behaviors; genes that either protect people from developing cancer or put them at greater risk; and genes that either aid or thwart cancer treatment.
The goals of such research, Levin says, are to be able to:
- Predict those people who might be most susceptible to smoking and to help them resist smoking initiation;
- Provide more effective cessation assistance to those who are already smoking;
- Help prevent development of cancer by use of chemoprevention strategies;
- Understand the biological processes that make some smokers more susceptible to different cancers; and
- Offer tailored treatments based on tumor and genetic profiles in each patient to help prevent further disease.
If such a global program can reduce tobacco-related cancers, then the same approach might work for cancers influenced by poor nutrition, lack of exercise and excess body weight, and other such factors, Levin says. Add in prevention screening and it makes sense why Levin says "the future of cancer prevention is an integrated approach."
Biobehavior in the cancer formula
Two facts about smokers rivet cancer researchers: the notion that not everyone who tries cigarettes becomes addicted, and the knowledge that only a fraction of long-term smokers (about 15%) will develop lung cancer, although tobacco also is responsible for one-third of all cardiovascular deaths under age 85.
Innate differences exist between non-smokers and smokers in terms of "biobehavior," such as a need for nicotine, the way different societal cultures view smoking and how they respond to clinical treatment. Within the division's three groups - the Department of Health Disparities Research, the Department of Behavioral Science and the Department of Epidemiology - are investigating aspects of these topics, often in collaboration.
Differences also are likely between smokers in their physiological responses - how their bodies vary in susceptibility to the cancer-causing compounds in cigarettes - which implies that agents might be designed that help prevent cancer from developing or treat it more effectively if it does. To explore these topics, other teams of researchers in the Department of Epidemiology and the Department of Clinical Cancer Prevention are working together.
The Department of Behavioral Science is unique in the United States, says its chair clinical psychologist Ellen R. Gritz, Ph.D. "It is a fully established department, with resources and faculty, as opposed to a program, which many cancer centers have."
This department "focuses on the human side of cancer - the continuum from risk behaviors that cause or contribute to cancer to the psychosocial factors that affect treatment outcome, adjustment and survival," Gritz says.
"Our goal in smoking-related research is to detect those who are susceptible to nicotine, identify the best ways to prevent these persons from beginning to smoke and, if they do, determine how best to break the nicotine addiction that can result," Gritz says.
The Department's longstanding efforts in this field have helped the institution enroll thousands of smokers in numerous smoking cessation studies.