Oncology – Cancer Medicine Explained

What Is Oncology?

Oncology is a major medical specialty focused on cancer -- a broad term for diseases caused by the uncontrolled growth and spread of abnormal cells. The word derives from the Greek onkos (mass, tumor) and logos (study). Oncologists are physicians who specialize in diagnosing and treating cancer, guiding patients through all stages of their illness from initial detection to recovery or palliative care.

Cancer is not a single disease but an umbrella term for more than 100 distinct conditions, all sharing the characteristic of abnormal, unregulated cell division that can invade surrounding tissues or spread to distant organs through a process called metastasis.

Subspecialties of Oncology

Oncology encompasses several specialized fields:

• Medical Oncology: Treatment of cancer using systemic therapies such as chemotherapy, immunotherapy, and targeted agents.
• Surgical Oncology: Removal of tumors and affected tissues through surgery.
• Radiation Oncology: Use of ionizing radiation to destroy cancer cells or shrink tumors.
• Pediatric Oncology: Cancer diagnosis and treatment in children and adolescents.
• Gynecologic Oncology: Cancers of the female reproductive system.
• Hematologic Oncology: Blood and lymphatic cancers such as leukemia and lymphoma.
• Palliative Oncology: Management of symptoms and quality of life in advanced cancer.

Causes of Cancer

Cancer develops through a complex, multi-step process in which genetic mutations cause cells to lose normal growth control. Key risk factors include:

• Genetic predisposition: Inherited mutations, such as BRCA1/BRCA2 (breast and ovarian cancer).
• Environmental exposures: UV radiation, ionizing radiation, chemical carcinogens, and air pollution.
• Lifestyle factors: Tobacco use, excessive alcohol consumption, obesity, physical inactivity, and poor diet.
• Infections: Certain viruses and bacteria, such as human papillomavirus (HPV) in cervical cancer, or Helicobacter pylori in stomach cancer.
• Age: The risk of most cancers increases with advancing age.

Symptoms and Warning Signs

Cancer can present very differently depending on the organ affected and the stage of disease. Common warning signs include:

• Unexplained or persistent weight loss
• Unusual lumps or swellings
• Persistent fatigue and exhaustion
• Changes in skin, moles, or mucous membranes
• Persistent cough, hoarseness, or difficulty swallowing
• Unexplained bleeding or unusual discharge
• Persistent pain without a clear cause

These symptoms can also be caused by non-cancerous conditions, but persistent or worsening symptoms should always be evaluated by a medical professional.

Diagnosis

Oncological diagnosis involves a range of tools to detect and characterize cancer as accurately as possible:

• Imaging: Ultrasound, X-ray, CT (computed tomography), MRI (magnetic resonance imaging), and PET-CT (positron emission tomography).
• Laboratory tests: Blood counts and tumor markers -- proteins in the blood that may indicate tumor activity.
• Biopsy: Removal and microscopic examination of tissue samples to confirm diagnosis.
• Molecular and genetic testing: Analysis of mutations in tumor tissue to guide targeted therapy decisions.
• Staging: Determining the extent and spread of cancer, typically using the TNM system (Tumor, Nodes, Metastasis).

Treatment

Cancer treatment is typically multidisciplinary and tailored to the individual patient, the cancer type, and its stage. Major treatment modalities include:

Surgery

Surgical removal of the tumor is the primary treatment for many solid cancers, especially when the disease is localized and has not spread to distant organs.

Radiation Therapy

High-energy radiation damages the DNA of cancer cells, preventing them from dividing. It can be used with curative intent or to relieve symptoms in advanced disease.

Drug-Based Therapies

• Chemotherapy: Cytotoxic drugs that kill rapidly dividing cells throughout the body.
• Targeted therapy: Drugs designed to interfere with specific molecular targets present in cancer cells.
• Immunotherapy: Treatments that harness the body's immune system to recognize and destroy cancer cells, including checkpoint inhibitors.
• Hormone therapy: Blocking hormone signaling in hormone-sensitive cancers such as breast and prostate cancer.

Stem Cell Transplantation

Used primarily for blood cancers, healthy stem cells are transplanted to restore bone marrow function after high-dose chemotherapy.

Prevention and Early Detection

Early detection significantly improves survival rates. Established screening programs include colonoscopy (colorectal cancer), mammography (breast cancer), Pap smear (cervical cancer), and skin cancer checks. Vaccination against HPV can reduce the risk of several HPV-related cancers. Lifestyle modifications -- such as not smoking, maintaining a healthy weight, and limiting alcohol -- also play a key role in cancer prevention.

References

1. World Health Organization (WHO): Cancer. Fact Sheet. Available at: https://www.who.int/news-room/fact-sheets/detail/cancer (accessed 2024).
2. National Cancer Institute (NCI): What Is Cancer? Available at: https://www.cancer.gov/about-cancer/understanding/what-is-cancer (accessed 2024).
3. DeVita, V.T., Lawrence, T.S., Rosenberg, S.A.: DeVita, Hellman, and Rosenberg's Cancer: Principles and Practice of Oncology. 11th edition. Wolters Kluwer, 2019.