cancer

cancer
Name	Cancer
Synonyms	Malignant tumor, malignant neoplasm
Caption	A histological image of adenocarcinoma cells.
Field	Oncology
Symptoms	Lump, abnormal bleeding, prolonged cough, unexplained weight loss, change in bowel movements
Complications	Metastasis, paraneoplastic syndrome
Onset	Any age, risk increases with age
Duration	Chronic
Types	Carcinoma, sarcoma, lymphoma, leukemia, glioma
Causes	Tobacco smoking, obesity, poor diet, lack of physical activity, excessive alcohol consumption, certain infections, ionizing radiation, environmental pollutants
Risks	Ageing, genetics
Diagnosis	Biopsy, medical imaging
Prevention	Not smoking, maintaining a healthy weight, limiting alcohol, eating plenty of vegetables, fruits, and whole grains, vaccination against certain infectious diseases, avoiding excessive sunlight exposure
Treatment	Surgery, radiation therapy, chemotherapy, targeted therapy, immunotherapy
Medication	Cisplatin, doxorubicin, pembrolizumab
Prognosis	Varies widely by type and stage
Frequency	~20 million new cases per year globally
Deaths	~10 million per year globally

cancer. It is a group of diseases characterized by the uncontrolled growth and spread of abnormal cells. If this spread is not controlled, it can result in death, making it a leading cause of mortality worldwide. The disease arises from the transformation of normal cells into tumor cells in a multi-stage process that generally progresses from a pre-cancerous lesion to a malignant tumor.

Overview

The fundamental abnormality resulting in the development of cancer is the continual unregulated proliferation of cells. These cells can invade adjacent parts of the body, a process known as invasion, and can also spread to distant organs through the bloodstream or lymphatic system, a process termed metastasis. Major categories include carcinoma, which arises from epithelial cells, and sarcoma, originating from connective tissue. Other principal types are leukemia, lymphoma, and glioma, which affect blood, the immune system, and the brain, respectively. The study and treatment of these diseases is the field of oncology.

Causes and risk factors

External agents, known as carcinogens, can initiate or promote development. These include physical carcinogens like ultraviolet and ionizing radiation; chemical carcinogens such as components of tobacco smoke, aflatoxin (a food contaminant), and arsenic (a drinking water contaminant); and biological carcinogens like infections from certain viruses, bacteria, or parasites. Key risk factors are tobacco use, alcohol consumption, an unhealthy diet, and physical inactivity. The World Health Organization lists these among the leading preventable risks. Certain inflammatory conditions and inherited genetic mutations, such as those in BRCA1 and BRCA2, also significantly increase susceptibility.

Pathophysiology

The disease process begins with damage to DNA within a cell, often due to environmental insults or errors in replication. Critical genes affected are oncogenes, which promote cell growth, and tumor suppressor genes, which inhibit it. Mutations that activate oncogenes, like RAS or MYC, or inactivate tumor suppressors, such as TP53 or APC, allow cells to evade normal growth controls. These cells also acquire the ability to induce angiogenesis, resist cell death, and avoid immune destruction, as outlined in the hallmarks framework proposed by researchers like Douglas Hanahan and Robert Weinberg.

Diagnosis

Suspicion often arises from symptoms or screening tests. Definitive diagnosis typically requires examination of tissue under a microscope by a pathologist following a biopsy or surgical excision. Medical imaging techniques, including X-ray, computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and ultrasound, are used to locate a tumor and determine if it has spread. Blood tests can detect tumor markers, such as prostate-specific antigen (PSA) for prostate cancer, or circulating tumor cells, though these are not definitive alone.

Treatment

The choice of therapy depends on the type, location, and stage of the disease, as well as the patient's health. Common modalities include surgery with the goal of complete removal, radiation therapy using high-energy rays to destroy cells, and chemotherapy using cytotoxic drugs like cisplatin and doxorubicin. More recent approaches involve targeted therapy, which attacks specific molecular abnormalities (e.g., imatinib for chronic myeloid leukemia), and immunotherapy, which harnesses the patient's immune system (e.g., pembrolizumab). Treatment is often administered at specialized centers like the MD Anderson Cancer Center or the Memorial Sloan Kettering Cancer Center.

Epidemiology

It is a leading cause of death globally, accounting for nearly 10 million deaths in 2020 according to the World Health Organization. The most common types in men are lung cancer, prostate cancer, and colorectal cancer; in women, they are breast cancer, lung cancer, and colorectal cancer. Incidence and mortality rates vary significantly by geographic region and level of human development, influenced by factors like the prevalence of tobacco smoking, access to screening programs such as mammography, and availability of treatments. The International Agency for Research on Cancer (IARC) monitors global trends.

Research directions

Ongoing investigations focus on understanding the genetic and molecular basis of the disease through projects like The Cancer Genome Atlas. Efforts in precision medicine aim to tailor treatments based on the genetic profile of an individual's tumor. Immunotherapy research continues to expand, exploring new checkpoint inhibitors and CAR-T cell therapy. Prevention studies evaluate the efficacy of vaccines, such as those against human papillomavirus (HPV) and hepatitis B virus (HBV). Major funding and coordination come from organizations like the National Cancer Institute (NCI) and the American Cancer Society.

Category:Diseases and disorders Category:Causes of death