Harrison's Internal Medicine Chapter 78. Prevention and Early Detection of Cancer
Prevention and Early Detection of Cancer: Introduction Improved understanding of carcinogenesis has allowed cancer prevention and early detection (also known as cancer control) to expand beyond the identification and avoidance of carcinogens. Specific interventions to prevent cancer in those at risk, and more sensitive and specific screening for early detection of cancer are the goals.
I am very grateful to the special group of distinguished scientists who made up the Panel
and Secretariat for this major review of the evidence on food, nutrition, physical activity
and cancer. The vision of WCRF International in convening this Panel and confidence in
letting a strong-willed group of scientists have their way is to be highly commended.
In our view, the evidence reviewed here that led to our recommendations provides a
wonderful opportunity to prevent cancer and improve global health. Individuals and
populations have in their hands the means to lead fuller, healthier lives.
Cancer Chemoprevention Chemoprevention involves the use of specific natural or synthetic chemical agents to reverse, suppress, or prevent carcinogenesis before the development of invasive malignancy.
Cancer develops through an accumulation of genetic and epigenetic changes that are potential points of intervention to prevent cancer. The initial changes are termed initiation. The alteration can be inherited or acquired through the action of physical, infectious, or chemical carcinogens.
Improved understanding of carcinogenesis has allowed cancer prevention and early detection (also known as cancer control) to expand beyond the identification and avoidance of carcinogens. Specific interventions to prevent cancer in those at risk, and more sensitive and specific screening for early detection of cancer are the goals. Carcinogenesis is not simply an event but a process, a continuum of discrete cellular changes over time resulting in more autonomous cellular processes.
There is growing evidence on the importance of studies focusing on mechanisms and
strategies leading to cancer prevention. The plethora of approaches include regulation
of oxidative stress using antioxidant therapies, carefully balanced diets and living
habits, epidemiological evidence and molecular approaches on the role of key
biological molecules such as antioxidant enzymes, vitamins, proteins and naturally
occurring free radical scavengers as well as controversial results and clinical
applications. These are some of the topics that this book highlights.
Since the first edition of Breast Cancer: Prognosis, Treatment and Prevention was
published there has been a tremendous amount of new information related to the basic
and clinical applications of this disease which can affect 1 of 8 people in the USA and
1 of 12 in European countries.
Prostate cancer treatment dates back almost
100 years. However, in an era of rapid developments
and innovations in cancer research and
uro-oncology, there is an increasing need to
update our knowledge and especially to guide
our practice by innovations and evidence-based
medicine. Prostate cancer is still evolving following
improvements in disease detection and
better understanding of disease characteristics.
Harrison's Internal Medicine Chapter 82. Infections in Patients with Cancer
Infections in Patients with Cancer: Introduction Infections are a common cause of death and an even more common cause of morbidity in patients with a wide variety of neoplasms. Autopsy studies show that most deaths from acute leukemia and half of deaths from lymphoma are caused directly by infection. With more intensive chemotherapy, patients with solid tumors have also become more likely to die of infection.
recommendations for evidence-based screening (Table 4-3). In addition to these population-based guidelines, it is reasonable to consider family and social history to identify individuals with special risk (www.ahrq.gov/clinic/uspstfix.htm). For example, when there is a significant family history of breast, colon, or prostate cancer, it is prudent to initiate screening about 10 years before the age when the youngest family member developed cancer.
The goal of cancer treatment is first to eradicate the cancer. If this primary goal cannot be accomplished, the goal of cancer treatment shifts to palliation, the amelioration of symptoms, and preservation of quality of life while striving to extend life. The dictum primum non nocere is not the guiding principle of cancer therapy. When cure of cancer is possible, cancer treatments may be undertaken despite the certainty of severe and perhaps life-threatening toxicities.
This book deals with problems which are sufficiently important to become the subject of studies.
Cancer of the stomach remains one of the most pressing medical problems. Meanwhile,
scientific and practical interest in this problem has markedly diminished during recent years.
According to some experts, this can be explained first by the decreasing incidence of gastric
cancer. But this concerns only some developed countries, where effective measures are taken
for the prevention and early diagnosis of malignant tumors.
In the past 15 years, molecular biologists and geneticists have uncovered
some of the most basic mechanisms by means of which normal stem cells
in a certain organ or tissue develop into cancerous tumors. This biological
knowledge serves as a basis for various models of carcinogenesis.
Cervical cancer is the second most prevalent cancer among women worldwide, and infection with Human Papilloma Virus (HPV) has been identified as the causal agent for this condition. The natural history of cervical cancer is characterized by slow disease progression, rendering the condition in essence preventable and even treatable when diagnosed in early stages.
Methods of Measuring Health Benefits
It is not practical to perform all possible screening procedures. For example, screening for laryngeal cancer in smokers is not currently recommended. It is necessary to examine the strength of evidence in favor of screening measures relative to the cost and risk of false-positive tests.
Screening is performed earlier and more frequently when there is a strong
family history. Randomized, controlled trials have documented that fecal occult blood testing (FOBT) confers a 15 to 30% reduction in colon cancer mortality. Although randomized trials have not been performed for sigmoidoscopy or colonoscopy, well-designed case-control studies suggest similar or greater efficacy relative to FOBT.
In the future, Pap smear frequency may be influenced by HPV testing and
the HPV vaccine.
Breast self-examination, clinical breast examination by a care giver, and mammography have been advocated as useful screening tools. Only screening mammography alone and screening mammography with clinical examination have been evaluated in randomized controlled trials. MRI is being assessed and is more accurate than mammography in women at high risk due to genetic predisposition or in women with very dense breast tissue.
hydrophobic compounds and thereby act as lipophilic antioxidants preventing
polyunsaturated fatty acids from oxidative damages. In fact, carotenoids are incorporated
into lipid membranes and thus could act as chain-breaking antioxidants by stopping free
radical chain reactions (propagation of lipid peroxidation), scavenging lipid peroxyl radicals
(LOO•), avoiding the abstraction of allylic hydrogens from neighboring lipids. Inactivation
of lipoxygenase activity by carotenoids is also proposed as another mechanism of protection
against oxidative stress.
We were able to obtain satisfactory postoperative PSA levels by RTUR-PCa comparable with
open radical prostatectomy. But we recently started to think that, after a considerable
number of the procedures, minimal residual prostate tissue at the part where cancer was not
detected by biopsy might not necessarily prevent the radicality of the disease in carefully
selected patients. We performed prostate biopsy to get information about the localization of
cancer. The results of cancer localization from operative specimens were consistent with
those from biopsy specimens in 46.7%....