What laboratory tests should be ordered for an adult patient with potential risk factors for cancer, such as family history or unexplained symptoms, to screen for cancer?

Laboratory Testing for Cancer Screening

There is no universal "cancer screening lab panel" recommended for asymptomatic patients without specific risk factors or symptoms, and routine laboratory testing for cancer detection in the general population is not supported by current guidelines. 1, 2, 3

The Evidence Against Routine Cancer Lab Screening

The fundamental problem with ordering labs to "check for cancer" is that accepted cancer screening requires evidence of mortality reduction in randomized controlled trials, not just the ability to detect disease. 2, 4 Most laboratory tests lack the sensitivity and specificity needed for effective cancer screening and lead to more harm than benefit through false positives, overdiagnosis, and unnecessary interventions. 5, 2

When Laboratory Testing IS Appropriate

Laboratory testing for cancer should be symptom-driven or risk-stratified, not performed as general screening:

For Patients with High-Risk Symptoms

If your patient has concerning symptoms, specific labs may be warranted:

• Unexplained weight loss, fever, or night sweats: Complete blood count (CBC) with differential to evaluate for hematologic malignancies 1, 6
• Jaundice: Liver function tests, bilirubin levels (predictive of pancreaticobiliary malignancy) 6
• Bone pain: Alkaline phosphatase, calcium levels to evaluate for metastatic disease 1
• Monocyte percentage >7% or platelet count >440×10⁹/L: These are independent predictors of cancer diagnosis in patients with clinical suspicion 6

For Patients with Established Cancer Diagnoses

• CEA (carcinoembryonic antigen): Only for surveillance in patients with diagnosed colorectal cancer (T2 or greater), measured every 3-6 months for 2 years, then every 6 months for total of 5 years 7
• PSA (prostate-specific antigen): Only after shared decision-making in men age 50+ with ≥10-year life expectancy, not as a general screening test 1, 8

For Patients Requiring Genetic Testing

Germline genetic testing is indicated for specific cancer diagnoses or strong family histories, NOT as general screening: 7

• Triple-negative breast cancer diagnosed ≤60 years: BRCA1/BRCA2 testing 7
• Epithelial ovarian, fallopian tube, or primary peritoneal cancer: BRCA1/BRCA2 testing 7
• Colorectal or endometrial cancer with mismatch repair deficiency: MLH1/MSH2/MSH6/PMS2/EPCAM testing 7
• Strong family history (first- or second-degree relatives with early-onset cancers): Multi-gene panel testing should include genes relevant to the family's cancer pattern 7

What to Do Instead of Ordering Labs

Focus on evidence-based cancer screening modalities that actually reduce mortality:

Age-Appropriate Screening (No Labs Required)

• Colorectal cancer (age 50+): Colonoscopy every 10 years OR annual fecal immunochemical testing (FIT) 1, 9
• Breast cancer (women age 40+): Annual mammography 1
• Cervical cancer (age 21+): Pap smear with or without HPV testing 1
• Lung cancer (age 55-80 with ≥30 pack-year history): Low-dose CT annually 2

Family History Collection

All patients should have a comprehensive cancer family history documented, including: 7

• First-degree relatives (parents, siblings, children) with cancer diagnoses and age at diagnosis
• Second-degree relatives (grandparents, aunts/uncles, nieces/nephews, half-siblings) with cancer diagnoses and age at diagnosis
• Ethnicity (particularly Ashkenazi Jewish ancestry for BRCA mutations) 7
• Any known hereditary cancer syndromes or prior genetic testing in the family 7

Common Pitfalls to Avoid

• Do not order tumor markers (CA-125, CA 19-9, AFP, etc.) as screening tests in asymptomatic patients - they have poor sensitivity/specificity and lead to unnecessary workups 5, 4
• Do not order "comprehensive metabolic panels" expecting to find cancer - abnormalities are nonspecific and do not constitute cancer screening 2, 4
• Do not confuse screening tests with diagnostic tests - labs ordered because of symptoms or clinical suspicion are diagnostic, not screening 4
• Do not bypass evidence-based screening (colonoscopy, mammography) in favor of blood tests - no blood test has been shown to reduce cancer mortality in average-risk populations 2, 3

The Bottom Line

If your patient is asymptomatic and average-risk, order age-appropriate imaging-based screening (colonoscopy, mammography) and take a detailed family history - do not order laboratory tests. 1, 2, 3 If your patient has concerning symptoms, order labs targeted to those specific symptoms, not a general "cancer panel." 6 If your patient has a strong family history or meets criteria for hereditary cancer syndromes, refer for genetic counseling and germline testing of specific genes. 7