**Cancer Basics:**
– Etymology and Definitions: The term ‘cancer’ originates from ancient Greek and refers to abnormal cell growth with the potential to invade or spread.
– Characteristics of Cancer: All tumor cells exhibit six hallmarks of cancer necessary for malignancy, including unregulated growth and tissue invasion.
– Causes: 90-95% of cancers result from genetic mutations due to environmental and lifestyle factors, with the remaining 5-10% due to inherited genetics.
**Symptoms and Impact:**
– Signs and Symptoms: Symptoms of cancer vary based on the tumor’s location, and post-diagnosis, individuals may experience anxiety or depression.
– Local Symptoms: Specific symptoms depend on the cancer type and location, with examples like lung cancer causing cough or pneumonia.
– Systemic Symptoms: Fatigue, weight loss, and skin changes may occur due to the body’s response to cancer, with certain cancers causing cachexia and persistent fever.
– Global Impact: In 2019, there were 24 million new cancer cases worldwide, with an annual death toll of 10 million, and the global economic cost estimated at $1.16 trillion per year.
**Metastasis and Management:**
– Metastasis: The spread of cancer to other body locations, leading to metastatic tumors, is a significant cause of cancer-related deaths.
– Chemotherapy drugs and medications like azathioprine can increase cancer risk, and recent treatments show promise in managing metastatic cancer.
– Early detection improves cancer cure rates, but metastatic cancer is harder to treat.
**Risk Factors:**
– Chemicals: Lung cancer is highly correlated with smoking, and certain chemicals like asbestos fibers or PFOA increase cancer risk.
– Diet and Exercise: Diet, physical inactivity, and obesity contribute to a significant percentage of cancer deaths, with some foods linked to specific cancers.
– Infection: Approximately 18% of cancer deaths worldwide are related to infectious diseases, with viruses like HPV and hepatitis B/C causing cancer.
– Radiation: Ultraviolet radiation, ionizing radiation, and residential exposure to radon gas are risk factors for cancer.
**Genetic and Cellular Mechanisms:**
– Genetic Changes in Cancer: Normal cell to cancer cell transformation requires altered genes regulating cell growth, with mutations, deletions, and translocations playing a role.
– Factors Contributing to Cancer Development: Errors in DNA replication, environmental factors, and mutations in cell signaling can accelerate cancer development.
– Clonal Evolution in Cancer Development: Initial errors in cells lead to compounding mutations, driving cancer progression and complicating treatment strategies.
– Epigenetics in Cancer: Epigenetic alterations regulate gene expression without changing DNA sequence, affecting DNA repair genes and increasing mutation rates in cancers.
– Role of DNA Damage and Repair in Carcinogenesis: Epigenetic defects in DNA repair genes contribute to cancer progression, increasing mutation frequencies and cancer risks.
This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. (March 2024) |
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in bowel movements. While these symptoms may indicate cancer, they can also have other causes. Over 100 types of cancers affect humans.
| Cancer | |
|---|---|
| Other names | Malignant tumor, malignant neoplasm |
 | |
| A coronal CT scan showing a malignant mesothelioma Legend: → tumor ←, ✱ central pleural effusion, 1 & 3 lungs, 2 spine, 4 ribs, 5 aorta, 6 spleen, 7 & 8 kidneys, 9 liver | |
| Pronunciation | |
| Specialty | Oncology |
| Symptoms | Lump, abnormal bleeding, prolonged cough, unexplained weight loss, change in bowel movements |
| Risk factors | Exposure to carcinogens, tobacco, obesity, poor diet, lack of physical activity, excessive alcohol, certain infections |
| Treatment | Radiation therapy, surgery, chemotherapy, targeted therapy |
| Prognosis | Average five-year survival 66% (USA) |
| Frequency | 24 million annually (2019) |
| Deaths | 10 million annually (2019) |
Tobacco use is the cause of about 22% of cancer deaths. Another 10% are due to obesity, poor diet, lack of physical activity or excessive alcohol consumption. Other factors include certain infections, exposure to ionizing radiation, and environmental pollutants. Infection with specific viruses, bacteria and parasites is an environmental factor causing approximately 16-18% of cancers worldwide. These infectious agents include Helicobacter pylori, hepatitis B, hepatitis C, human papillomavirus infection, Epstein–Barr virus, Human T-lymphotropic virus 1, Kaposi's sarcoma-associated herpesvirus and Merkel cell polyomavirus. Human immunodeficiency virus (HIV) does not directly cause cancer but it causes immune deficiency that can magnify the risk due to other infections, sometimes up to several thousand fold (in the case of Kaposi's sarcoma). Importantly, vaccination against hepatitis B and human papillomavirus have been shown to nearly eliminate risk of cancers caused by these viruses in persons successfully vaccinated prior to infection.
These environmental factors act, at least partly, by changing the genes of a cell. Typically, many genetic changes are required before cancer develops. Approximately 5–10% of cancers are due to inherited genetic defects. Cancer can be detected by certain signs and symptoms or screening tests. It is then typically further investigated by medical imaging and confirmed by biopsy.
The risk of developing certain cancers can be reduced by not smoking, maintaining a healthy weight, limiting alcohol intake, eating plenty of vegetables, fruits, and whole grains, vaccination against certain infectious diseases, limiting consumption of processed meat and red meat, and limiting exposure to direct sunlight. Early detection through screening is useful for cervical and colorectal cancer. The benefits of screening for breast cancer are controversial. Cancer is often treated with some combination of radiation therapy, surgery, chemotherapy and targeted therapy. Pain and symptom management are an important part of care. Palliative care is particularly important in people with advanced disease. The chance of survival depends on the type of cancer and extent of disease at the start of treatment. In children under 15 at diagnosis, the five-year survival rate in the developed world is on average 80%. For cancer in the United States, the average five-year survival rate is 66% for all ages.
In 2015, about 90.5 million people worldwide had cancer. 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% and 21%, respectively.
The most common types of cancer in males are lung cancer, prostate cancer, colorectal cancer, and stomach cancer. 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% 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. Rates are 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 US$1.16 trillion (equivalent to $1.62 trillion in 2023) per year as of 2010[update].