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Cancer: the story on HearLore | HearLore
Cancer
The word cancer originates from the ancient Greek term karkinos, meaning crab, a name bestowed by Hippocrates over two thousand years ago because the swollen veins around a tumor resembled the legs of a crustacean. This visual metaphor defined the disease for centuries, yet the reality of the illness was far more terrifying than the name suggested. For most of human history, cancer was a death sentence with no understanding of its cause, leaving patients to suffer from what was once called the cancer poison. The earliest written record of the disease appears in the Edwin Smith Papyrus, an Egyptian text from around 1600 BC that describes breast cancer, marking the beginning of a medical struggle that has persisted through every era of human existence. In the 17th century, the physician John Hill made the startling observation that tobacco sniffing caused nose cancer, a finding that would later be expanded upon by Percivall Pott in 1775 when he identified chimney sweeps' carcinoma, a cancer of the scrotum common among those who worked in soot-filled chimneys. These early observations laid the groundwork for understanding that external environmental factors could trigger the disease, a concept that would eventually revolutionize medicine. The history of cancer treatment is a testament to human resilience, evolving from the purgatives recommended by Galen in the 2nd century AD to the complex surgical interventions and radiation therapies of the modern era. Despite these advancements, the disease remains a formidable adversary, with over 100 distinct types affecting humans and causing approximately 10 million deaths worldwide in 2019 alone. The global economic cost of cancer reached an estimated 1.16 trillion US dollars per year, highlighting the immense burden the disease places on societies and individuals alike. As the population ages and lifestyle changes occur, particularly in the developing world, the incidence of cancer continues to rise, making it the leading cause of death in developed nations and the second leading cause in developing nations. The story of cancer is not just one of biological mystery but also of human ingenuity, fear, and the relentless pursuit of a cure.
The Silent Rebellion Within
Cancer is fundamentally a disease of tissue growth regulation, a rebellion within the body where normal cells transform into malignant ones through a series of genetic mutations. For a normal cell to become cancerous, the genes that regulate cell growth and differentiation must be altered, a process that typically requires multiple changes to occur over time. These genetic changes can happen at different levels, including the gain or loss of entire chromosomes, mutations in the nucleotide sequence of genomic DNA, or large-scale deletions and insertions. A well-known example of such a mutation is the Philadelphia chromosome, a translocation of chromosomes 9 and 22 that occurs in chronic myelogenous leukemia and results in the production of the BCR-abl fusion protein, an oncogenic tyrosine kinase. The transformation of a normal cell into a cancer cell is akin to a chain reaction caused by initial errors, which compound into more severe errors, each progressively allowing the cell to escape more controls that limit normal tissue growth. This rebellion-like scenario is an undesirable survival of the fittest, where the driving forces of evolution work against the body's design and enforcement of order. Once cancer has begun to develop, this ongoing process, termed clonal evolution, drives progression towards more invasive stages. Characteristic abilities developed by cancers include evasion of apoptosis, self-sufficiency in growth signals, insensitivity to anti-growth signals, sustained angiogenesis, limitless replicative potential, metastasis, reprogramming of energy metabolism, and evasion of immune destruction. The classical view of cancer is a set of diseases driven by progressive genetic abnormalities, but a role for epigenetic alterations was identified in the early 21st century. Epigenetic alterations are functionally relevant modifications to the genome that do not change the nucleotide sequence, such as changes in DNA methylation, histone modification, and changes in chromosomal architecture. These changes may remain through cell divisions, endure for multiple generations, and can be considered as equivalent to mutations. When DNA repair is deficient, DNA damage remains in cells at a higher than usual level, causing increased frequencies of mutation and/or epimutation. Individuals with an inherited impairment in any of 34 DNA repair genes have increased cancer risk, with some defects ensuring a 100% lifetime chance of cancer, such as p53 mutations. However, such germline mutations are the cause of only about 1 percent of cancers, while in sporadic cancers, deficiencies in DNA repair are much more frequently caused by epigenetic alterations that reduce or silence expression of DNA repair genes.
Common questions
What is the origin of the word cancer?
The word cancer originates from the ancient Greek term karkinos, meaning crab, a name bestowed by Hippocrates over two thousand years ago because the swollen veins around a tumor resembled the legs of a crustacean.
When was the earliest written record of cancer documented?
The earliest written record of the disease appears in the Edwin Smith Papyrus, an Egyptian text from around 1600 BC that describes breast cancer, marking the beginning of a medical struggle that has persisted through every era of human existence.
What percentage of cancer cases are due to environmental and lifestyle factors?
The majority of cancers, some 90 to 95 percent of cases, are due to genetic mutations from environmental and lifestyle factors rather than inherited genetics.
How many people died from cancer worldwide in 2019?
In 2019, there were 10 million deaths worldwide from cancer, representing over the previous decade increases of 21 percent.
Which specific genetic mutation is known as the Philadelphia chromosome?
The Philadelphia chromosome is a translocation of chromosomes 9 and 22 that occurs in chronic myelogenous leukemia and results in the production of the BCR-abl fusion protein, an oncogenic tyrosine kinase.
What is the global economic cost of cancer per year?
The global economic cost of cancer reached an estimated 1.16 trillion US dollars per year, highlighting the immense burden the disease places on societies and individuals alike.
The majority of cancers, some 90 to 95 percent of cases, are due to genetic mutations from environmental and lifestyle factors rather than inherited genetics. Tobacco smoke, for example, causes 90 percent of lung cancer and contains over fifty known carcinogens, including nitrosamines and polycyclic aromatic hydrocarbons. Tobacco is responsible for about one in five cancer deaths worldwide and about one in three in the developed world, with lung cancer death rates in the United States mirroring smoking patterns, showing dramatic increases followed by decreases as smoking rates have changed since the 1950s. Alcohol increases the risk of cancer of the breast, throat, liver, esophagus, mouth, larynx, and colon, with 10 percent of cancers in males and 3 percent of cancers in females in Western Europe attributed to alcohol exposure. Diet and obesity are related to up to 30 to 35 percent of cancer deaths, with excess body weight associated with the development of many types of cancer and a factor in 14 to 20 percent of cancer deaths in the United States. A high-salt diet is linked to gastric cancer, while aflatoxin B1, a frequent food contaminant, causes liver cancer, and betel nut chewing can cause oral cancer. National differences in dietary practices may partly explain differences in cancer incidence, with gastric cancer more common in Japan due to its high-salt diet and colon cancer more common in the United States. Immigrant cancer profiles mirror those of their new country, often within one generation, suggesting that environmental factors play a more significant role than previously thought. Infections account for approximately 18 percent of cancer deaths worldwide, ranging from a high of 25 percent in Africa to less than 10 percent in the developed world. Viruses are the usual infectious agents that cause cancer, including human papillomavirus, Epstein-Barr virus, Kaposi's sarcoma herpesvirus, hepatitis B and hepatitis C viruses, and Human T-cell leukemia virus-1. Bacterial infection may also increase the risk of cancer, as seen in Helicobacter pylori-induced gastric carcinoma, and parasitic infections such as Schistosoma haematobium can cause squamous cell carcinoma of the bladder. Radiation exposure, including ultraviolet radiation and radioactive material, is a risk factor for cancer, with residential exposure to radon gas having similar cancer risks as passive smoking. Ionizing radiation is not a particularly strong mutagen but is a more potent source of cancer when combined with other cancer-causing agents, such as radon plus tobacco smoke. Prolonged exposure to ultraviolet radiation from the sun can lead to melanoma and other skin malignancies, with clear evidence establishing ultraviolet radiation, especially the non-ionizing medium wave UVB, as the cause of most non-melanoma skin cancers.
The Battle For Survival
In 2019, annual cancer cases grew by 23.6 million people, and there were 10 million deaths worldwide, representing over the previous decade increases of 26 percent and 21 percent, respectively. The most common types of cancer in males are lung cancer, prostate cancer, colorectal cancer, and stomach cancer, while in females, the most common types are breast cancer, colorectal cancer, lung cancer, and cervical cancer. If skin cancer other than melanoma were included in total new cancer cases each year, it would account for around 40 percent of cases. In children, acute lymphoblastic leukemia and brain tumors are most common, except in Africa, where non-Hodgkin lymphoma occurs more often. In 2012, about 165,000 children under 15 years of age were diagnosed with cancer. The risk of cancer increases significantly with age, and many cancers occur more commonly in developed countries, with rates increasing as more people live to an old age and as lifestyle changes occur in the developing world. The global total economic costs of cancer were estimated at 1.16 trillion US dollars per year, with the total health care expenditure on cancer in the US estimated to be 80.2 billion US dollars in 2015. Cancer causes also costs for informal care, with indirect costs and informal care costs typically estimated to exceed or equal the health care costs of cancer. The three most common childhood cancers are leukemia, brain tumors, and lymphomas, with cancer affecting about 1 in 285 children in the United States. Rates of childhood cancer increased by 0.6 percent per year between 1975 and 2002 in the United States and by 1.1 percent per year between 1978 and 1997 in Europe, while death from childhood cancer decreased by half between 1975 and 2010 in the United States. Although it is possible for cancer to strike at any age, most patients with invasive cancer are over 65, and according to cancer researcher Robert A. Weinberg, if we lived long enough, sooner or later we all would get cancer. Some slow-growing cancers are particularly common but often are not fatal, with autopsy studies in Europe and Asia showing that up to 36 percent of people have undiagnosed and apparently harmless thyroid cancer at the time of their deaths and that 80 percent of men develop prostate cancer by age 80. As these cancers do not cause the patient's death, identifying them would have represented overdiagnosis rather than useful medical care. The total health care expenditure on cancer in the US was estimated to be 80.2 billion US dollars in 2015, and even though cancer-related health care expenditure have increased in absolute terms during recent decades, the share of health expenditure devoted to cancer treatment has remained close to 5 percent between the 1960s and 2004. A similar pattern has been observed in Europe where about 6
The Global Burden And Future
percent of all health care expenditure are spent on cancer treatment. In addition to health care expenditure and financial toxicity, cancer causes indirect costs in the form of productivity losses due to sick days, permanent incapacity and disability as well as premature death during working age. Cancer causes also costs for informal care, with indirect costs and informal care costs typically estimated to exceed or equal the health care costs of cancer. A study found women were around six times more likely to be divorced soon after a diagnosis of cancer compared to men, with the rate of separation for cancer-survivors showing correlations with race, age, income, and comorbidities in a study.