CancerEdit

Cancer is a broad group of diseases characterized by the unchecked growth of abnormal cells that can invade adjacent tissues and spread to distant sites (metastasis). It encompasses many distinct disorders arising from genetic mutations, environmental exposures, and aging, with solid tumors such as carcinomas and sarcomas, as well as hematologic cancers like leukemias and lymphomas. Despite remarkable advances in science and medicine, cancer remains a leading cause of death worldwide, reflecting the complexity of biology, the variety of cancer subtypes, and the challenges of detection and treatment across populations. The struggle against cancer rests on a mix of basic research, clinical care, and public health policy, with substantial contributions from the private sector, charitable organizations, and government-funded institutions that support innovation and access to care.

The disease is not a single condition but a family of diseases defined by unregulated cell growth, immune evasion, and the ability to metastasize. Cancers are often categorized by tissue of origin (for example, breast, colon, or lung cancer) or by their cellular characteristics (such as adenocarcinoma or melanoma). Advances in molecular biology have revealed that the same cancer type can harbor multiple distinct genetic drivers, which in turn influence prognosis and treatment options. For readers seeking broader context, oncology is the branch of medicine that studies cancer and its treatment, while cancer biology explores the cellular and molecular mechanisms that underlie cancer development.

Causes and risk factors

Cancer arises from a combination of inherited susceptibility, environmental exposures, and stochastic genetic changes that accumulate over time. While some cancers run in families due to specific genetic syndromes, most cases reflect a complex interplay of risk factors rather than a single cause.

Genetic predisposition: Certain inherited mutations increase the risk of specific cancers. Individuals with familial syndromes may develop cancers at younger ages or have tumors in multiple organ systems. Work in genetics and related fields helps identify high-risk groups and tailor screening and prevention strategies.
Tobacco and other carcinogens: Tobacco use remains a major preventable cause of several cancers, notably lung cancer, but also cancers of the mouth, throat, bladder, and more. Other environmental carcinogens include occupational exposures (such as asbestos) and ultraviolet radiation from sun exposure.
Infections: Persistent infections contribute to cancer risk in some contexts. For example, certain strains of human papillomavirus (HPV) are linked to cervical and oropharyngeal cancers, while hepatitis B and C viruses are associated with liver cancer. Vaccination and antiviral therapies can reduce these risks.
Diet, obesity, and physical activity: Diet quality, body weight, and physical activity influence cancer risk for some malignancies. While these factors do not guarantee occurrence, they shape population-level risk and are common targets for public health guidance.
Age and biology: The risk of many cancers increases with age as cells accumulate mutations and tissue repair processes change. Age is a major risk factor across many cancer types, influencing both incidence and treatment considerations.
Pediatric cancers: Childhood cancers often arise from different biological mechanisms than many adult cancers and require specialized approaches in diagnosis and care. See pediatric cancer for a focused discussion.
Disparities and access: Socioeconomic status, access to screening, and timely care influence cancer outcomes. Efforts to reduce disparities focus on improving access and delivering evidence-based prevention and treatment.

Detection and screening

Early detection improves outcomes for several cancers, but screening strategies involve weighing benefits against potential harms, costs, and the risks of overdiagnosis.

Screening tests: Population screening programs use tests such as imaging, cytology, and molecular assays to identify cancers at an early, more treatable stage. Well-established examples include mammography for breast cancer and colonoscopy for colorectal cancer. Cervical cancer screening has relied on Pap testing and, more recently, high-risk HPV testing. In high-risk populations, low-dose computed tomography (LDCT) is used to screen for lung cancer.
Diagnostic confirmation: Abnormal screening results typically lead to diagnostic confirmation through procedures such as biopsy and histopathological assessment, often complemented by imaging and genomic profiling to determine the cancer’s characteristics and likely behavior.
Staging and prognosis: Once cancer is diagnosed, its stage and molecular features guide prognosis and treatment choices. The TNM system and other staging frameworks help clinicians categorize disease extent and plan management.
Controversies in screening: Debates surround overdiagnosis and false positives in some screening programs, particularly for certain age groups or cancer types. Critics argue that screening can lead to unnecessary procedures and anxiety, while proponents emphasize lives saved through early detection. Policy decisions often emphasize evidence-based screening intervals, risk stratification, and patient-centered decision making. See discussions of screening in the context of public health policy and cost-effectiveness considerations.

Classification and biology

Cancers are grouped by tissue of origin and by their molecular and histological features, which influence behavior and treatment response.

Solid tumors: Carcinomas (arising from epithelial cells) and sarcomas (from connective tissues) are common categories of solid tumors. Subtypes vary widely in behavior and treatment sensitivity.
Hematologic cancers: Leukaemias, lymphomas, and myelomas originate in blood-forming tissues or immune cells and have distinct patterns of spread and response to therapy.
Molecular drivers: Cancers are increasingly classified by their genetic alterations, such as oncogene activation or tumor suppressor gene inactivation. This molecular view underpins approaches in precision oncology, where therapies target specific abnormalities within a patient’s tumor.
Targeted therapies and immunotherapy: Treatments aimed at particular molecular targets or at harnessing the immune system have transformed outcomes for several cancer types. See targeted therapy and immunotherapy for more detail.
Psychosocial and quality-of-life considerations: Beyond tumor biology, patient well-being, treatment tolerance, and symptom management play central roles in care plans. Resources in palliative care support patients and families through advanced disease stages.

Treatments

Cancer care typically involves a combination of local and systemic approaches, selected to maximize effectiveness while considering patient preferences and overall health.

Local therapies:
- Surgery: Resection of tumors remains central for many solid cancers, especially when disease is localized.
- Radiotherapy: Ionizing radiation is used to destroy cancer cells, either as a primary treatment or in conjunction with surgery and/or systemic therapy.
Systemic therapies:
- Chemotherapy: Drugs that kill dividing cells can be effective across several cancer types, though they can cause significant side effects.
- Targeted therapy: Treatments that inhibit specific molecular abnormalities in tumors have improved outcomes for certain cancers and often carry different side effect profiles than conventional chemotherapy.
- Immunotherapy: Strategies that stimulate or restore the immune system’s ability to recognize and attack cancer cells have produced durable responses in some patients.
- Hormone therapy: Some cancers depend on hormones for growth and can be slowed or halted with hormonal manipulation.
Emerging approaches:
- Precision oncology: Tailoring treatment based on the tumor’s genetic and molecular features aims to improve efficacy and reduce unnecessary toxicity.
- Combination regimens: Integrating several modalities—surgery, radiation, and systemic therapy—can enhance outcomes for complex cases.
Access, cost, and value: The high cost of modern cancer therapies raises debates about affordability, price controls, and value-based pricing. Policymakers, insurers, and health systems work to balance patient access with sustaining innovation. See health policy and drug pricing discussions for broader context.

Public health, economics, and policy

Economic and policy choices influence cancer prevention, detection, and care at the population level. A practical approach emphasizes evidence, patient choice, and sustainable financing.

Prevention and vaccination: Public health measures—from tobacco control to vaccines against cancer-causing infections like HPV—can reduce the burden of disease. Programs that encourage healthy lifestyles remain a priority in many systems.
Screening policy and access: Decisions about which populations to screen, at what ages, and with which tests hinge on evidence of benefit, harms, and cost-effectiveness. Efficient screening programs can save lives while avoiding unnecessary procedures and anxiety.
Health care delivery: A mix of public and private components often underpins access to screening, diagnosis, and treatment. Private hospitals, clinics, and nonprofit providers frequently contribute to capacity, innovation, and patient-centered care, while government programs set standards, regulate safety, and fund essential services.
Research funding and incentives: Investments in basic science and clinical research fuel advances in prevention, diagnosis, and treatment. The patent system and competitive markets are credited with sustaining discovery, though policy debates continue about balancing incentives with affordable patient access.
Equity and disparities: Differences in cancer outcomes across populations reflect a blend of biology, access to care, and social determinants. Policies aim to improve early detection and access to high-quality treatment for all, with attention to evidence-based strategies rather than branding or identity-driven approaches.
Controversies in policy and public discourse: Critics of interventions that tie funding to broad identity-based metrics argue for policies grounded in clinical effectiveness and measurable outcomes. Proponents contend that addressing disparities and ensuring access are essential for a just, prosperous society. In this context, discussions about risk factors, screening, and treatment should prioritize solid evidence and avoid overreliance on rhetoric that lacks support from clinical data.

History and milestones

Cancer research has progressed through eras of observation, surgical advancement, and molecular breakthroughs. Early surgical techniques evolved into multimodal strategies combining local control with systemic therapies. The discovery of oncogenes and tumor suppressor genes, the advent of radiation and chemotherapy, and later the rise of immunotherapy and precision medicine have reshaped prognosis for many cancers. Notable milestones include the development of screening programs, the mapping of cancer genomes, and the translation of laboratory findings into targeted drugs that address specific molecular drivers.