Prognosis
See also: List of cancer mortality rates in the United States and Cancer survivor
Cancer has a reputation as a deadly disease. Taken as a whole, about half of people receiving treatment for invasive cancer (excluding carcinoma in situ and non-melanoma skin cancers) die from cancer or its treatment.[19] Survival is worse in the developing world,[19] partly because the types of cancer that are most common there are at present harder to treat than those associated with the lifestyle of developed countries.[152] However, the survival rates vary dramatically by type of cancer, and by the stage at which it is diagnosed, with the range running from the great majority of people surviving to almost no one surviving as long as five years after diagnosis. Once a cancer has metastasized or spread beyond its original site, the prognosis normally becomes much worse.
Those who survive cancer are at increased risk of developing a second primary cancer at about twice the rate of those never diagnosed with cancer.[153] The increased risk is believed to be primarily due to the same risk factors that produced the first cancer, partly due to the treatment for the first cancer, and potentially related to better compliance with screening.[153]
Predicting either short-term or long-term survival is difficult and depends on many factors. The most important factors are the particular kind of cancer and the patient's age and overall health. People who are frail with many other health problems have lower survival rates than otherwise healthy people. A centenarian is unlikely to survive for five years even if the treatment is successful. People who report a higher quality of life tend to survive longer.[154] People with lower quality of life may be affected by major depressive disorder and other complications from cancer treatment and/or disease progression that both impairs their quality of life and reduces their quantity of life. Additionally, patients with worse prognoses may be depressed or report a lower quality of life directly because they correctly perceive that their condition is likely to be fatal.
People with cancer, even those who are walking on their own, have an increased risk of blood clots in veins. The use ofheparin appears improve survival and decrease the risk of blood clots.[155]
Epidemiology
Main article: Epidemiology of cancer
See also: List of countries by cancer rate
In 2008, approximately 12.7 million cancers were diagnosed (excluding non-melanoma skin cancers and other non-invasive cancers),[19] and in 2010 nearly 7.98 million people died.[157] Cancers as a group account for approximately 13% of all deaths each year with the most common being: lung cancer (1.4 million deaths),stomach cancer (740,000 deaths), liver cancer (700,000 deaths), colorectal cancer(610,000 deaths), and breast cancer (460,000 deaths).[158] This makes invasive cancer the leading cause of death in the developed world and the second leading cause of death in the developing world.[19] Over half of cases occur in the developing world.[19]
Deaths from cancer were 5.8 million in 1990[157] and rates have been increasing primarily due to an aging population and lifestyle changes in the developing world.[19] The most significant risk factor for developing cancer is old age.[159]Although it is possible for cancer to strike at any age, most people who are diagnosed with invasive cancer are over the age of 65.[159] According to cancer researcher Robert A. Weinberg, "If we lived long enough, sooner or later we all would get cancer."[160] Some of the association between aging and cancer is attributed to immunosenescence,[161] errors accumulated in DNA over a lifetime,[162] and age-related changes in the endocrine system.[163] The effect of aging on cancer is complicated with a number of factors such as DNA damage and inflammation promoting it and a number of factors such as vascular aging and endocrine changes inhibiting it.[164]
Some slow-growing cancers are particularly common. Autopsy studies in Europe and Asia have shown that up to 36% of people have undiagnosed and apparently harmless thyroid cancer at the time of their deaths, and that 80% of men developprostate cancer by age 80.[165][166] As these cancers did not cause the person's death, identifying them would have represented overdiagnosis rather than useful medical care.
The three most common childhood cancers are leukemia (34%), brain tumors (23%), and lymphomas (12%).[167] In the United States cancer affects about 1 in 285 children.[168] Rates of childhood cancer have increased by 0.6% per year between 1975 to 2002 in the United States[169] and by 1.1% per year between 1978 and 1997 in Europe.[167] Death from childhood cancer have decreased by half since 1975 in the United States.[168]
History
Main article: History of cancer
Cancer has existed for all of human history.[170] The earliest written record regarding cancer is from circa 1600 BC in the Egyptian Edwin Smith Papyrus and describes cancer of the breast.[170] Hippocrates (ca. 460 BC – ca. 370 BC) described several kinds of cancer, referring to them with the Greek word καρκίνοςkarkinos (crab or crayfish).[170] This name comes from the appearance of the cut surface of a solid malignant tumor, with "the veins stretched on all sides as the animal the crab has its feet, whence it derives its name".[171] Galen stated that "cancer of the breast is so called because of the fancied resemblance to a crab given by the lateral prolongations of the tumor and the adjacent distended veins".[172]:738 Celsus (ca. 25 BC – 50 AD) translated karkinos into the Latin cancer, also meaning crab and recommended surgery as treatment.[170] Galen (2nd century AD) disagreed with the use of surgery and recommended purgatives instead.[170] These recommendations largely stood for 1000 years.[170]
In the 15th, 16th and 17th centuries, it became acceptable for doctors to dissect bodies to discover the cause of death.[173]The German professor Wilhelm Fabry believed that breast cancer was caused by a milk clot in a mammary duct. The Dutch professor Francois de la Boe Sylvius, a follower of Descartes, believed that all disease was the outcome of chemical processes, and that acidic lymph fluid was the cause of cancer. His contemporary Nicolaes Tulp believed that cancer was a poison that slowly spreads, and concluded that it was contagious.[174]
The physician John Hill described tobacco snuff as the cause of nose cancer in 1761.[173] This was followed by the report in 1775 by British surgeon Percivall Pott that chimney sweeps' carcinoma, a cancer of the scrotum, was a common disease among chimney sweeps.[175] With the widespread use of the microscope in the 18th century, it was discovered that the 'cancer poison' spread from the primary tumor through the lymph nodes to other sites ("metastasis"). This view of the disease was first formulated by the English surgeon Campbell De Morgan between 1871 and 1874.[176]
Society and culture
Though many diseases (such as heart failure) may have a worse prognosis than most cases of cancer, cancer is the subject of widespread fear and taboos. The euphemism "after a long illness" is still commonly used (2012), reflecting an apparent stigma.[177] This deep belief that cancer is necessarily a difficult and usually deadly disease is reflected in the systems chosen by society to compile cancer statistics: the most common form of cancer—non-melanoma skin cancers, accounting for about one-third of all cancer cases worldwide, but very few deaths[178][179]—are excluded from cancer statistics specifically because they are easily treated and almost always cured, often in a single, short, outpatient procedure.[180]
Cancer is regarded as a disease that must be "fought" to end the "civil insurrection"; a War on Cancer has been declared. Military metaphors are particularly common in descriptions of cancer's human effects, and they emphasize both the parlous state of the affected individual's health and the need for the individual to take immediate, decisive actions himself, rather than to delay, to ignore, or to rely entirely on others caring for him. The military metaphors also help rationalize radical, destructive treatments.[181][182]
In the 1970s, a relatively popular alternative cancer treatment was a specialized form of talk therapy, based on the idea that cancer was caused by a bad attitude.[183] People with a "cancer personality"—depressed, repressed, self-loathing, and afraid to express their emotions—were believed to have manifested cancer through subconscious desire. Some psychotherapists said that treatment to change the patient's outlook on life would cure the cancer.[183] Among other effects, this belief allows society to blame the victim for having caused the cancer (by "wanting" it) or having prevented its cure (by not becoming a sufficiently happy, fearless, and loving person).[184] It also increases patients' anxiety, as they incorrectly believe that natural emotions of sadness, anger or fear shorten their lives.[184] The idea was excoriated by the notoriously outspoken Susan Sontag, who published Illness as Metaphor while recovering from treatment for breast cancer in 1978.[183]Although the original idea is now generally regarded as nonsense, the idea partly persists in a reduced form with a widespread, but incorrect, belief that deliberately cultivating a habit of positive thinking will increase survival.[184] This notion is particularly strong in breast cancer culture.[184]
One idea about why people with cancer are blamed or stigmatized, called the just-world hypothesis, is that blaming cancer on the patient's actions or attitudes allows the blamers to regain a sense of control. This is based upon the blamers' belief that the world is fundamentally just, and so any dangerous illness, like cancer, must be a type of punishment for bad choices, because in a just world, bad things would not happen to good people.[185]
Economic effect
In 2007, the overall costs of cancer in the U.S. — including treatment and indirect mortality expenses (such as lost productivity in the workplace) — was estimated to be $226.8 billion. In 2009, 32% of Hispanics and 10% of children 17 years old or younger lacked health insurance; "uninsured patients and those from ethnic minorities are substantially more likely to be diagnosed with cancer at a later stage, when treatment can be more extensive and more costly."[186]
Research
Main article: Cancer research
Because cancer is a class of diseases,[187][188] it is unlikely that there will ever be a single "cure for cancer" any more than there will be a single treatment for all infectious diseases.[189] Angiogenesis inhibitors were once thought to have potential as a "silver bullet" treatment applicable to many types of cancer, but this has not been the case in practice.[190] It is more likely that angiogenesis inhibitors and other cancer therapeutics will be used in combination to reduce cancer morbidity and mortality.[191]
Experimental cancer treatments are treatments that are being studied to see whether they work. Typically, these are studied in clinical trials to compare the proposed treatment to the best existing treatment. They may be entirely new treatments, or they may be treatments that have been used successfully in one type of cancer, and are now being tested to see whether they are effective in another type.[192] More and more, such treatments are being developed alongside companion diagnostic tests to target the right drugs to the right patients, based on their individual biology.[193]
Cancer research is the intense scientific effort to understand disease processes and discover possible therapies.
Research about cancer causes focuses on the following issues:
- Agents (e.g. viruses) and events (e.g. mutations) that cause or facilitate genetic changes in cells destined to become cancer.
- The precise nature of the genetic damage, and the genes that are affected by it.
- The consequences of those genetic changes on the biology of the cell, both in generating the defining properties of a cancer cell, and in facilitating additional genetic events that lead to further progression of the cancer.
The improved understanding of molecular biology and cellular biology due to cancer research has led to a number of new treatments for cancer since U.S. President Nixon declared the "War on Cancer" in 1971. Since then, the U.S. has spent over $200 billion on cancer research, including resources from the public and private sectors and foundations.[194] During that time, the country has seen a five percent decrease in the cancer death rate (adjusting for size and age of the population) between 1950 and 2005.[195]
Hypercompetition for the financial resources that are required to conduct science appears to suppress the creativity, cooperation, risk-taking, and original thinking required to make fundamental discoveries, unduly favoring low-risk research into small incremental advancements over innovative research that might discover radically new and dramatically improved therapy. Other consequences of the highly pressured competition for research resources appear to be a substantial number of research publications whose results cannot be replicated, and perverse incentives in research funding that encourage grantee institutions to grow without making sufficient investments in their own faculty and facilities.[196][197][198][199]
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