Oncology

Intermediate

Oncology is the branch of medicine devoted to the study, diagnosis, treatment, and prevention of cancer. Cancer arises when normal cells undergo genetic mutations that disrupt the regulatory mechanisms governing cell growth and division, leading to uncontrolled proliferation and the potential to invade surrounding tissues or spread to distant organs through a process called metastasis. Oncology encompasses a vast spectrum of malignancies, from common solid tumors such as breast, lung, and colorectal cancers to hematologic malignancies including leukemias, lymphomas, and myelomas.

The discipline is traditionally divided into three major clinical specialties: medical oncology, which focuses on systemic therapies such as chemotherapy, targeted therapy, immunotherapy, and hormonal therapy; surgical oncology, which involves the operative removal of tumors and surrounding tissue; and radiation oncology, which uses ionizing radiation to destroy cancer cells or shrink tumors. Modern oncology increasingly relies on a multidisciplinary team approach, integrating pathology, radiology, genetics, palliative care, and psychosocial support to deliver comprehensive patient-centered care.

The field has undergone revolutionary advances in the twenty-first century. The completion of the Human Genome Project and the advent of next-generation sequencing have enabled precision oncology, where treatment is tailored to the molecular profile of an individual's tumor rather than solely its anatomical site. Immunotherapy, particularly immune checkpoint inhibitors targeting PD-1, PD-L1, and CTLA-4, has transformed outcomes for previously intractable cancers such as melanoma and non-small cell lung cancer. CAR-T cell therapy, liquid biopsies, and artificial intelligence-driven diagnostics represent the frontier of a field that continues to redefine what is possible in the fight against cancer.

Practice a little. See where you stand.

Ready to practice?5 minutes. No pressure.

Take the Quiz Learn First

Quiz

Reveal what you know — and what needs work

Adaptive Learn

Responds to how you reason, with real-time hints

Start here

Flashcards

Build recall through spaced, active review

Cheat Sheet

The essentials at a glance — exam-ready

Glossary

Master the vocabulary that unlocks understanding

Learning Roadmap

A structured path from foundations to mastery

Book

Deep-dive guide with worked examples

Key Concepts

The multistep biological process by which normal cells are transformed into cancer cells through the accumulation of genetic and epigenetic alterations. It typically involves initiation (DNA damage), promotion (clonal expansion), and progression (invasion and metastasis).

Example

Chronic exposure to tobacco smoke causes sequential mutations in lung epithelial cells, first producing dysplasia, then carcinoma in situ, and ultimately invasive lung cancer over a period of years to decades.

The process by which cancer cells spread from the primary tumor to distant organs through the bloodstream or lymphatic system. Metastasis is responsible for approximately 90% of cancer-related deaths and involves a complex cascade of invasion, intravasation, survival in circulation, extravasation, and colonization.

Example

Breast cancer commonly metastasizes to bone, liver, lung, and brain. A patient initially treated for breast cancer may present years later with back pain caused by metastatic lesions in the spine.

A standardized classification system that describes the extent of cancer based on Tumor size and local extent (T), regional lymph Node involvement (N), and distant Metastasis (M). Staging guides treatment decisions and provides prognostic information.

Example

A colon cancer classified as T3N1M0 indicates the tumor has grown through the muscle layer of the colon wall (T3), spread to one to three regional lymph nodes (N1), but has no distant metastasis (M0), corresponding to Stage III disease.

A class of immunotherapy drugs that block inhibitory proteins (checkpoints) on immune cells or cancer cells, thereby unleashing the immune system to recognize and attack tumors. Key targets include PD-1, PD-L1, and CTLA-4.

Example

Pembrolizumab (Keytruda), a PD-1 inhibitor, dramatically improved survival in advanced melanoma and is now approved for multiple cancer types including lung, head and neck, and bladder cancers.

An approach to cancer treatment that uses genomic profiling and molecular analysis of a patient's tumor to identify specific driver mutations and select targeted therapies most likely to be effective for that individual's cancer.

Example

A patient with non-small cell lung cancer whose tumor harbors an EGFR exon 19 deletion receives osimertinib, a targeted EGFR inhibitor, rather than conventional chemotherapy, resulting in better response rates and fewer side effects.

The complex ecosystem surrounding a tumor, consisting of blood vessels, immune cells, fibroblasts, signaling molecules, and extracellular matrix. The microenvironment plays a critical role in tumor growth, immune evasion, and response to therapy.

Example

Tumors described as 'immune hot' have high infiltration of cytotoxic T cells and tend to respond well to checkpoint inhibitors, while 'immune cold' tumors with few immune cells often resist immunotherapy.

Oncogenes are mutated forms of normal genes (proto-oncogenes) that promote uncontrolled cell growth when activated. Tumor suppressor genes normally restrain cell division, and their loss of function through mutation contributes to cancer development.

Example

The TP53 gene is the most commonly mutated tumor suppressor in human cancers, found altered in over 50% of all malignancies. The HER2 oncogene is amplified in about 20% of breast cancers and is targeted by trastuzumab (Herceptin).

The use of cytotoxic drugs to kill rapidly dividing cancer cells or inhibit their growth. Chemotherapy agents work through various mechanisms including DNA damage, inhibition of DNA synthesis, and disruption of mitotic spindle formation. They often affect normal rapidly dividing cells as well, leading to side effects.

Example

The FOLFOX regimen (folinic acid, fluorouracil, and oxaliplatin) is a standard adjuvant chemotherapy protocol for stage III colon cancer, reducing the risk of recurrence by approximately 20% compared to surgery alone.

Chimeric Antigen Receptor T-cell therapy is a form of adoptive cell therapy in which a patient's own T cells are genetically engineered to express a synthetic receptor that targets a specific protein on cancer cells. The modified cells are expanded in the laboratory and infused back into the patient.

Example

Tisagenlecleucel (Kymriah) targets the CD19 protein on B cells and has achieved complete remission rates of approximately 80% in pediatric patients with relapsed or refractory acute lymphoblastic leukemia.

The use of tests, imaging, or procedures to detect cancer in asymptomatic individuals before symptoms develop, when treatment is most effective. Effective screening programs require that the cancer has a detectable preclinical phase and that early treatment improves outcomes.

Example

Low-dose CT screening for lung cancer in high-risk smokers reduces lung cancer mortality by approximately 20%. Colonoscopy screening detects and removes precancerous polyps, preventing colorectal cancer entirely in many cases.

One concept at a time.

Explore your way

Choose a different way to engage with this topic — no grading, just richer thinking.

Explore your way — choose one:

Explore with AI →

Curriculum alignment— Standards-aligned

Grade level

College+

Learning objectives

•Analyze the molecular mechanisms of carcinogenesis including oncogene activation, tumor suppressor loss, and genomic instability
•Evaluate staging systems and prognostic biomarkers used to guide treatment selection for solid and hematologic malignancies
•Apply principles of chemotherapy, radiation therapy, and immunotherapy to explain their mechanisms and clinical indications
•Compare targeted therapy approaches including monoclonal antibodies, kinase inhibitors, and CAR-T cell therapy for cancer treatment

Recommended Resources

This page contains affiliate links. We may earn a commission at no extra cost to you.

Books

The Emperor of All Maladies: A Biography of Cancer

by Siddhartha Mukherjee

DeVita, Hellman, and Rosenberg's Cancer: Principles & Practice of Oncology

by Vincent T. DeVita Jr., Theodore S. Lawrence, Steven A. Rosenberg

The Biology of Cancer

by Robert A. Weinberg

Molecular Biology of the Cell

by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter

Courses

Introduction to the Biology of Cancer

CourseraEnroll

Cancer Biology

MIT OpenCourseWareEnroll

Fundamentals of Immunology: Innate Immunity and B-Cell Function

edXEnroll

My Progress Focus Mode

Interdisciplinary

Immunology

The study of the immune system, including its structure, function, and role in defending the body against infectious agents and disease.

Intermediate

STEM & Engineering

Genetics

Genetics is the study of genes, heredity, and genetic variation in living organisms, encompassing topics from Mendelian inheritance and DNA structure to modern genomics, gene editing, and their applications in medicine and biotechnology.

Intermediate

STEM & Engineering

Molecular Biology

The study of biological processes at the molecular level, focusing on DNA, RNA, and protein structures and their roles in gene expression and cellular function.

Intermediate

Interdisciplinary

Pharmacology

The science of how drugs interact with biological systems, encompassing drug mechanisms, therapeutic effects, adverse reactions, and the principles guiding rational medication use.

Intermediate

Oncology

Quiz

Adaptive Learn

Flashcards

Cheat Sheet

Glossary

Learning Roadmap

Book

Key Concepts

Carcinogenesis

Metastasis

Tumor Staging (TNM System)

Immune Checkpoint Inhibitors

Precision Oncology

Tumor Microenvironment

Oncogenes and Tumor Suppressor Genes

Chemotherapy

CAR-T Cell Therapy

Cancer Screening and Early Detection

Explore your way

Grade level

Learning objectives

Recommended Resources

Books

The Emperor of All Maladies: A Biography of Cancer

DeVita, Hellman, and Rosenberg's Cancer: Principles & Practice of Oncology

The Biology of Cancer

Molecular Biology of the Cell

Courses

Introduction to the Biology of Cancer

Cancer Biology

Fundamentals of Immunology: Innate Immunity and B-Cell Function

Related Topics

Immunology

Genetics

Molecular Biology

Pharmacology