Tumor Marker — Substances Indicating Cancer

Tumour markers encompass a broad spectrum of biochemical entities, including proteins, hormones, enzymes, and genetic fragments. While some markers are specific to a single type of cancer, many are elevated across several different malignancies. It is critical to recognise that benign conditions can also elevate these levels, meaning tumour markers are rarely used entirely in isolation for establishing a definitive diagnosis.

In modern clinical practice, tumour markers serve primarily as longitudinal tracking tools. By measuring baseline concentrations before therapy begins and tracking fluctuations over time, oncology teams gain valuable insight into whether an intervention is reducing tumour burden or if disease progression is occurring.

Tracking tumour markers provides an accessible, minimally invasive method to oversee disease kinetics between scheduled imaging scans. For patients undergoing active systemic therapy, a descending marker trajectory offers objective reassurance of therapeutic response. Conversely, an unexpected elevation can prompt timely diagnostic investigations, such as CT or PET scans, before physical symptoms re-emerge. Understanding your specific marker trends empowers informed, shared discussions with your clinical team throughout your care pathway.

Most conventional tumour markers are quantified via simple peripheral blood draws analysed in a clinical laboratory. Certain markers are evaluated directly in tumour tissue via immunohistochemistry or specialised molecular sequencing following a core biopsy or surgical resection. Routine serial testing is standard practice, as individual single-point measurements are less informative than longitudinal trends.

Tumour markers are evaluated across numerous malignancies. Common examples include prostate-specific antigen (PSA) in prostate cancer, carcinoembryonic antigen (CEA) in colorectal cancer, CA 125 in epithelial ovarian cancer, and CA 15-3 or CA 27-29 in breast cancer. Alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) are essential in testicular germ cell tumours and primary liver cancer.

Tumour marker dynamics directly influence therapeutic decision-making. A sustained drop during chemotherapy, endocrine therapy, or targeted therapy signals treatment efficacy, supporting continuation of the regimen. Rising values may prompt clinicians to change drug classes, adjust dosing, or consider clinical trials. However, treatment alterations are rarely based solely on markers without confirmatory radiological evidence.