Which of the following statements most correctly describes the utility of clinical laboratory assays for tumor markers?

• A. Tumor markers are useful to screen asymptomatic patients for tumors
• B. Tumor markers are highly specific
• C. Tumor markers indicate the likelihood of an individual developing a tumor
• D. Tumor markers are useful in tracking the efficacy of treatment

Answer: (D)

The main idea here is that tumor markers are used to follow how a cancer responds to therapy and to watch for recurrence, not to screen healthy people or predict who will develop cancer. Because most tumor markers lack perfect sensitivity and specificity, they’re not reliable for screening asymptomatic individuals. They can also be elevated for noncancer reasons, which limits their predictive value for developing a tumor.

Tracking treatment efficacy is where these markers shine. By measuring the marker level over time, clinicians can gauge whether the tumor burden is shrinking with therapy (level falls), remaining stable, or rising (possible progression or recurrence). This helps guide decisions about continuing, changing, or stopping treatment. Examples include using markers like CEA to monitor colorectal cancer or CA 125 for ovarian cancer, and PSA for prostate cancer progression.

In short, the strongest, most consistent use of tumor markers is to monitor disease course and response to treatment rather than to screen populations or predict who will develop a tumor.