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Tumor Markers

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Introduction & Classification - Cancer Detectives

  • Tumor Markers: Substances (proteins, enzymes, hormones) from cancer cells or body's response. Uses: aid diagnosis, stage, prognose, monitor therapy, detect recurrence. Limited for screening.
  • Ideal Characteristics: 📌 SENSITIVE & SPECIFIC
    • High sensitivity & specificity
    • Correlates with tumor burden
    • Reflects therapy response
    • Predicts recurrence
    • Easy, cost-effective
  • Classification:
    CategoryExamplesPrimary Association(s)
    EnzymesPSA, NSEProstate, Neuroendocrine
    HormoneshCG, CalcitoninGerm Cell, Medullary Thyroid Ca
    Oncofetal AgAFP, CEALiver/Germ Cell, GI Cancers
    Carbohydrate AgCA 125, CA 19-9Ovarian, Pancreatic

⭐ Most tumor markers lack sufficient specificity for widespread population screening; they are primarily valuable for monitoring disease progression or recurrence in diagnosed patients.

Common Markers: Set 1 - Key Player Trio

MarkerPrimary Associated Cancer(s)Other Associations/Key Clinical Notes
AFPHepatocellular Carcinoma (HCC), Non-seminomatous germ cell tumors (NSGCT) e.g., yolk sac tumor📌 A Foetus Protein. ↑ Physiological (pregnancy), pathological (neural tube defects, ataxia-telangiectasia). Normal: <10 ng/mL. Monitoring therapy & recurrence.
β-hCGChoriocarcinoma, Germ cell tumors (seminomatous & NSGCT), Hydatidiform mole↑ Normal pregnancy. β-subunit is specific. Used for diagnosis, prognosis, and monitoring response to therapy.
PSAProstate CancerOrgan-specific (prostate tissue), not cancer-specific. ↑ Benign Prostatic Hyperplasia (BPH), prostatitis, post-DRE. Levels: <4 ng/mL normal, 4-10 ng/mL grey zone, >10 ng/mL high risk. Screening, staging aid, monitoring.

Common Markers: Set 2 - CA & Hormonal IDs

MarkerPrimary Associated Cancer(s)Other Associations/Key Clinical Notes
CA-125Ovarian (epithelial) 📌Monitor response/recurrence. Normal <35 U/mL. Also ↑ in endometriosis, PID, pregnancy.
CA 19-9Pancreatic, GI 📌Cholangiocarcinoma. Monitor. Lewis (a-/b-) non-expressors.
CA 15-3/27.29Breast (metastatic) 📌Monitor therapy/recurrence. Also ↑ in benign breast disease, ovarian, lung cancer.
hCGGTD, Germ cell tumors (testicular, ovarian)β-hCG specific. Pregnancy detection.
CalcitoninMedullary Thyroid Carcinoma (MTC)Screening in MEN2 syndromes. Post-op monitoring for recurrence.

Clinical Application - Uses & Cautions

Uses (📌 SAD PMR):

  • Screening: Limited (e.g., PSA in high-risk groups).
  • Aid Diagnosis: Supplements clinical/imaging findings; not standalone.
  • Prognosis: Levels may correlate with tumor burden/aggressiveness.
  • Monitoring Therapy: Assess treatment response (serial measurements).
  • Detecting Recurrence: Early indicator of relapse post-treatment.

Limitations/Cautions:

  • Low sensitivity: False negatives, especially in early-stage disease.
  • Low specificity: False positives due to benign conditions (e.g., inflammation, smoking), physiological states.
  • Not all patients with a specific cancer show elevated markers.
  • Marker levels may not always correlate with tumor size or stage.
  • Hook effect (very high concentrations can give falsely low readings).

⭐ Serial measurements of a tumor marker are often more informative than a single value, reflecting trends over time.

High‑Yield Points - ⚡ Biggest Takeaways

  • AFP: For hepatocellular carcinoma & yolk sac tumors (non-seminomatous GCT).
  • β-hCG: For choriocarcinoma, moles, & many testicular germ cell tumors.
  • CEA: Monitors colorectal cancer recurrence; also in other adenocarcinomas.
  • CA-125: Tracks ovarian cancer (epithelial) response and detection.
  • CA 19-9: For pancreatic cancer & cholangiocarcinoma; aids prognosis.
  • PSA: Screens, diagnoses, & monitors prostate cancer activity.
  • Calcitonin: Highly specific for medullary thyroid carcinoma; screens MEN2_family_members_._

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Tryptase (enzyme)

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