Oncology Glossary
A comprehensive reference of key terms used throughout PipelineEvidence, covering drug classes, biomarkers, clinical trial concepts, and treatment approaches in modern oncology. Terms link to relevant tumor type pages where applicable.
35 terms defined
Adjuvant Therapy
Treatment given after the primary therapy (usually surgery) to reduce the risk of cancer recurrence. Examples include adjuvant chemotherapy for colon cancer after surgical resection or adjuvant immunotherapy for melanoma after resection.
Antibody-Drug Conjugate (ADC)
A targeted therapy that combines a monoclonal antibody with a cytotoxic drug payload, delivering chemotherapy directly to cancer cells that express the target antigen. Examples include trastuzumab deruxtecan (Enhertu), enfortumab vedotin (Padcev), and sacituzumab govitecan (Trodelvy). ADCs represent one of the fastest-growing drug classes in oncology.
Biomarker
A measurable biological characteristic used to assess disease status, predict prognosis, or guide treatment selection. In oncology, biomarkers include genetic mutations (e.g., BRCA1/2), protein expression levels (e.g., PD-L1, HER2), and molecular signatures (e.g., microsatellite instability). Comprehensive biomarker testing is increasingly essential for personalized cancer treatment.
Bispecific Antibody
An engineered antibody designed to simultaneously bind two different targets, typically a tumor antigen (e.g., CD20, BCMA) and a T-cell activator (CD3). By physically bridging cancer cells and immune cells, bispecific antibodies direct T-cell killing of tumor cells. FDA-approved examples include mosunetuzumab (for follicular lymphoma), teclistamab (for multiple myeloma), and tebentafusp (for uveal melanoma).
BRAF
A gene encoding the B-Raf protein kinase in the MAPK signaling pathway. The BRAF V600E mutation is an oncogenic driver in approximately 50% of melanomas, 60% of papillary thyroid cancers, 100% of hairy cell leukemias, and smaller subsets of lung cancer, colorectal cancer, and other malignancies. Targeted with BRAF inhibitors (vemurafenib, dabrafenib, encorafenib) often combined with MEK inhibitors.
BRCA1/BRCA2
Tumor suppressor genes involved in homologous recombination DNA repair. Germline mutations significantly increase lifetime risk of breast cancer (40-70%), ovarian cancer (20-40%), prostate cancer, and pancreatic cancer. BRCA-mutated cancers are sensitive to PARP inhibitors and platinum-based chemotherapy through the concept of synthetic lethality.
CAR-T Cell Therapy
Chimeric Antigen Receptor T-cell therapy involves collecting a patient's T cells, genetically engineering them to express a receptor targeting a specific cancer antigen, expanding them in the laboratory, and infusing them back into the patient. FDA-approved CAR-T products target CD19 (for lymphomas and ALL) or BCMA (for multiple myeloma). CAR-T therapy represents one of the most significant advances in cancer immunotherapy.
Checkpoint Inhibitor
A type of immunotherapy that blocks inhibitory immune checkpoint proteins (PD-1, PD-L1, CTLA-4, LAG-3) to restore T-cell anti-tumor activity. Checkpoint inhibitors have transformed the treatment of melanoma, lung cancer, bladder cancer, kidney cancer, and many other malignancies. Major drugs include pembrolizumab (Keytruda), nivolumab (Opdivo), atezolizumab (Tecentriq), and durvalumab (Imfinzi).
Clinical Trial Phases
Drug development progresses through sequential phases: Phase 1 tests safety and dosing in small numbers of patients; Phase 2 evaluates efficacy and side effects in a larger group; Phase 3 compares the new treatment to the current standard in large randomized trials; Phase 4 monitors long-term safety after FDA approval. Phase 3 results form the basis for most FDA approvals.
Combined Positive Score (CPS)
A method for scoring PD-L1 expression that counts PD-L1-positive tumor cells, lymphocytes, and macrophages relative to total tumor cells. CPS is used as a companion diagnostic for pembrolizumab in gastric, esophageal, cervical, head and neck, and other cancers. Higher CPS generally correlates with greater immunotherapy benefit.
Complete Response (CR)
The disappearance of all signs of cancer in response to treatment, as determined by imaging, laboratory tests, and/or physical examination. A complete response does not necessarily mean cure, as microscopic disease may remain undetected. Sustained complete response over time is associated with better long-term outcomes.
EGFR (Epidermal Growth Factor Receptor)
A transmembrane receptor tyrosine kinase frequently altered in cancer. Activating EGFR mutations (exon 19 deletions, L858R) drive approximately 15-20% of lung adenocarcinomas in Western populations and up to 50% in East Asian populations. Targeted with TKIs including osimertinib (Tagrisso), the current first-line standard. EGFR is also overexpressed in head and neck, colorectal, and other cancers.
FDA Approval
Authorization by the U.S. Food and Drug Administration for a drug to be marketed for a specific indication. Regular approval requires substantial evidence of efficacy (typically from phase 3 trials). Accelerated approval allows earlier access based on surrogate endpoints (e.g., tumor response rate) with post-marketing confirmatory trials required. Breakthrough therapy designation expedites development for serious conditions.
FGFR (Fibroblast Growth Factor Receptor)
A family of receptor tyrosine kinases (FGFR1-4) frequently altered in cancer through mutations, fusions, or amplifications. FGFR2 fusions occur in 10-16% of intrahepatic cholangiocarcinomas and are targeted by pemigatinib, futibatinib, and erdafitinib. FGFR3 mutations/fusions occur in bladder cancer. FGFR alterations represent important targetable drivers across multiple tumor types.
First-Line Therapy
The initial systemic treatment given for advanced or metastatic cancer. First-line therapy selection is typically based on tumor type, molecular profiling, patient fitness, and clinical trial evidence. Subsequent treatments after progression are called second-line, third-line, etc.
HER2 (Human Epidermal Growth Factor Receptor 2)
An oncogene that encodes a transmembrane receptor tyrosine kinase. HER2 overexpression or gene amplification occurs in approximately 15-20% of breast cancers, 15-20% of gastric/GEJ cancers, and smaller subsets of other tumor types. HER2-positive cancers are treated with targeted agents including trastuzumab, pertuzumab, trastuzumab deruxtecan (Enhertu), and tucatinib. HER2 testing is a mandatory component of breast and gastric cancer workup.
Homologous Recombination Deficiency (HRD)
Impairment in the homologous recombination DNA repair pathway, most commonly caused by BRCA1/2 mutations but also by alterations in RAD51C/D, PALB2, and other genes. HRD is found in approximately 50% of high-grade serous ovarian cancers and subsets of breast, prostate, and pancreatic cancers. HRD tumors are sensitive to PARP inhibitors and platinum chemotherapy.
Immunotherapy
Treatment that harnesses or enhances the immune system's ability to recognize and destroy cancer cells. Types include checkpoint inhibitors (most widely used), CAR-T cell therapy, bispecific antibodies, cancer vaccines, oncolytic viruses, and cytokines. Immunotherapy has transformed outcomes in melanoma, lung cancer, kidney cancer, and many other malignancies.
KRAS
An oncogene mutated in approximately 25% of all human cancers, including 90% of pancreatic cancers, 40% of colorectal cancers, and 25-30% of lung adenocarcinomas. KRAS was historically considered undruggable until the development of KRAS G12C inhibitors (sotorasib, adagrasib) and emerging KRAS G12D inhibitors, representing a major breakthrough in targeted therapy.
Microsatellite Instability (MSI)
A condition caused by defective DNA mismatch repair (dMMR) leading to accumulation of mutations at microsatellite regions throughout the genome. MSI-high/dMMR tumors have high mutational burden and generate abundant neoantigens, making them highly responsive to checkpoint immunotherapy. MSI-H occurs in approximately 15% of colorectal cancers, 30% of endometrial cancers, and smaller proportions of other tumor types. MSI testing also identifies potential Lynch syndrome.
Minimal Residual Disease (MRD)
Small numbers of cancer cells remaining after treatment that are undetectable by conventional methods (e.g., microscopy) but can be detected by sensitive techniques such as flow cytometry, PCR, or next-generation sequencing. MRD status is an important prognostic factor in leukemias and multiple myeloma, and is increasingly used to guide treatment decisions.
Molecular Profiling
Comprehensive analysis of a tumor's genetic alterations, gene expression patterns, and protein markers to guide treatment selection. Methods include next-generation sequencing (NGS), fluorescence in situ hybridization (FISH), immunohistochemistry (IHC), and circulating tumor DNA (ctDNA) analysis. Molecular profiling is now recommended at diagnosis for most advanced cancers.
Neoadjuvant Therapy
Treatment given before the primary therapy (usually surgery) to shrink tumors and improve surgical outcomes. Neoadjuvant approaches are standard in breast cancer, rectal cancer, esophageal cancer, and increasingly used in lung cancer, bladder cancer, and melanoma. Pathological response to neoadjuvant therapy is an important prognostic indicator.
NTRK Fusion
A gene rearrangement involving one of three neurotrophic tyrosine receptor kinase genes (NTRK1/2/3) that creates a constitutively active fusion protein driving tumor growth. NTRK fusions are rare (less than 1% of common cancers) but occur across many tumor types and are highly responsive to TRK inhibitors larotrectinib (Vitrakvi) and entrectinib (Rozlytrek), which received tumor-agnostic FDA approval.
Objective Response Rate (ORR)
The proportion of patients whose tumors shrink by at least 30% (partial response) or disappear completely (complete response) according to RECIST criteria. ORR is a common efficacy endpoint in clinical trials and is often used for accelerated FDA approval.
Overall Survival (OS)
The time from treatment initiation (or randomization in a clinical trial) until death from any cause. OS is considered the gold standard endpoint in oncology clinical trials because it is objective and clinically meaningful. Median OS represents the time at which 50% of patients have died.
PARP Inhibitor
A class of targeted therapy that blocks poly (ADP-ribose) polymerase enzymes involved in DNA repair. In cells with existing DNA repair defects (such as BRCA mutations), PARP inhibition causes lethal accumulation of DNA damage through synthetic lethality. FDA-approved PARP inhibitors include olaparib (Lynparza), niraparib (Zejula), rucaparib (Rubraca), and talazoparib (Talzenna).
PD-1/PD-L1
Programmed Death-1 (PD-1) is an immune checkpoint receptor on T cells; PD-L1 (Programmed Death-Ligand 1) is its ligand expressed on tumor cells and immune cells. When PD-L1 binds PD-1, it suppresses T-cell activity, allowing tumors to evade immune destruction. Anti-PD-1 antibodies (pembrolizumab, nivolumab) and anti-PD-L1 antibodies (atezolizumab, durvalumab, avelumab) block this interaction, restoring anti-tumor immunity.
Peptide Receptor Radionuclide Therapy (PRRT)
A targeted radionuclide therapy using radiolabeled somatostatin analogs (typically lutetium-177 dotatate/Lutathera) to deliver radiation directly to somatostatin receptor-expressing neuroendocrine tumor cells. PRRT is approved for progressive gastroenteropancreatic NETs based on the NETTER-1 trial.
Precision Medicine
An approach to cancer treatment that uses molecular profiling to match individual patients with the most effective therapies based on their tumor's specific genetic alterations. Also called personalized medicine or biomarker-directed therapy. Precision medicine has particularly transformed treatment of lung cancer, breast cancer, and hematologic malignancies.
Progression-Free Survival (PFS)
The time from treatment initiation until disease progression or death. PFS is a commonly used endpoint in clinical trials and is often available earlier than overall survival data. While PFS improvements do not always translate to OS benefit, large PFS improvements generally correlate with clinical benefit.
Synthetic Lethality
A concept where the combination of two genetic events results in cell death, while either alone is survivable. In cancer treatment, this principle is exploited by PARP inhibitors: cancer cells with BRCA mutations (one defective DNA repair pathway) cannot survive additional PARP inhibition (blocking a second repair pathway), while normal cells with intact BRCA function are spared.
Tumor Mutational Burden (TMB)
The total number of somatic mutations per megabase of DNA in a tumor. High TMB generates more neoantigens and is generally associated with greater immunotherapy benefit. TMB-high (≥10 mutations/megabase) is an FDA-approved biomarker for pembrolizumab across tumor types. Cancers with the highest TMB include melanoma, lung cancer, and bladder cancer.
Tyrosine Kinase Inhibitor (TKI)
A class of targeted therapy that blocks specific tyrosine kinase enzymes involved in cancer cell growth and survival signaling. TKIs are typically oral medications. Examples include imatinib (BCR-ABL for CML), osimertinib (EGFR for lung cancer), sunitinib and cabozantinib (multi-kinase for kidney cancer), and ibrutinib (BTK for CLL). TKIs have transformed treatment of CML, lung cancer, kidney cancer, and many other malignancies.
VEGF/VEGFR
Vascular endothelial growth factor (VEGF) and its receptors (VEGFR) drive tumor angiogenesis (new blood vessel formation). Anti-VEGF therapies include the antibody bevacizumab (Avastin) and multiple VEGFR-targeting TKIs (sunitinib, sorafenib, lenvatinib, cabozantinib). Anti-angiogenic therapy is a cornerstone of treatment for kidney cancer, liver cancer, colorectal cancer, and other tumor types.
Medical Disclaimer: This glossary is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Read full disclaimer.