Oncology

Oncology is the medical specialty dedicated to the study, diagnosis, and treatment of cancer — a group of diseases characterized by the uncontrolled growth and spread of abnormal cells. Medical oncologists specialize in systemic cancer treatments including chemotherapy, targeted therapy, immunotherapy, and hormonal therapy, working as part of multidisciplinary cancer care teams alongside surgical and radiation oncologists. Cancer is the second leading cause of death in the United States, with approximately 1.9 million new diagnoses annually. The most common cancers include breast, lung, colorectal, prostate, and melanoma. Medical oncologists manage the full spectrum from early-stage adjuvant therapy (preventing recurrence after surgery) to palliative treatment of metastatic disease. Immunotherapy has transformed oncology practice over the past decade. Checkpoint inhibitors — anti-PD-1 (pembrolizumab, nivolumab), anti-PD-L1 (atezolizumab, durvalumab), and anti-CTLA-4 (ipilimumab) — activate the immune system to attack cancer cells and have produced durable responses in melanoma, lung cancer, bladder cancer, and many other tumors. CAR-T cell therapy, in which a patient's own T cells are genetically engineered to target cancer antigens, has achieved remarkable remission rates in hematologic malignancies. Targeted therapy exploits specific genetic mutations driving tumor growth. EGFR inhibitors in lung adenocarcinoma, HER2-targeted therapy in breast and gastric cancer, BRAF inhibitors in melanoma, and BCR-ABL inhibitors (imatinib) in CML exemplify the precision oncology revolution. Precision medicine — enabled by next-generation sequencing of tumor DNA — allows oncologists to match patients to genotype-driven therapies regardless of tumor histology. Tumor mutational burden (TMB), microsatellite instability (MSI), and NTRK fusions are examples of biomarkers guiding treatment selection. Clinical trials, symptom management, survivorship care, and end-of-life planning are integral responsibilities of the medical oncologist.