From the Guidelines
In medullary thyroid cancer, the most important abnormal blood markers are elevated calcitonin and carcinoembryonic antigen (CEA) levels, which are used for diagnosis, monitoring treatment response, and detecting recurrence. These blood tests are crucial because medullary thyroid cancer doesn't concentrate radioactive iodine or produce thyroglobulin like differentiated thyroid cancers, making these traditional thyroid cancer markers less useful 1.
Key Blood Tests
- Calcitonin: produced by the parafollicular C cells of the thyroid that become cancerous in this condition
- Carcinoembryonic antigen (CEA): serves as an additional tumor marker
- Chromogranin A: another neuroendocrine tumor marker that may be elevated in some patients
- Calcium and parathyroid hormone levels: may be elevated in cases of hereditary medullary thyroid cancer associated with Multiple Endocrine Neoplasia type 2 (MEN2) due to hyperparathyroidism
- Catecholamines (metanephrines, normetanephrines): may be elevated in cases of hereditary medullary thyroid cancer associated with MEN2 due to associated pheochromocytomas 1
Importance of Blood Tests
These blood markers are valuable for monitoring treatment response and detecting recurrence, as well as for confirming hereditary forms of medullary thyroid cancer through genetic testing for RET proto-oncogene mutations 1.
Clinical Guidelines
According to clinical guidelines, measurements of serum markers calcitonin (and CEA in specific cases) and the calcitonin and CEA doubling times are of paramount importance in the post-surgical follow-up of patients with medullary thyroid cancer 1.
Follow-up
After total thyroidectomy, serum calcitonin level normalizes in 60%–90% of cases of patients with no lymph-node involvement, but only in 20% of those with lymph-node metastases 1. Serum calcitonin should be repeated every 6 months for the first 2–3 years and annually thereafter. Patients with biochemical remission after initial treatment have only a 3% chance of recurrence during long-term follow-up 1.
From the FDA Drug Label
Table 2: Per-Patient Incidence of Selected Laboratory Abnormalities in Patients with MTC Occurring at a Higher Incidence in CAPRELSA-Treated Patients (Between-Arm Difference of ≥5% [All Grades]*) Laboratory AbnormalitiesCAPRELSA 300 mgN=231PlaceboN=99 All Grades(%)Grade 3 or 4(%)All Grades(%)Grade 3 or 4(%)
- CTCAE version 3 was used to grade laboratory abnormalities Chemistries Hypocalcemia576253 ALT Increased512190 Hypoglycemia24071 Creatinine Increased16010 Hypomagnesemia7<120 Hematologic Neutropenia10<152 Thrombocytopenia9030
The blood tests that would be abnormal in medullary thyroid cancer include:
- Hypocalcemia: low calcium levels
- ALT Increased: elevated alanine transaminase levels
- Hypoglycemia: low blood sugar levels
- Creatinine Increased: elevated creatinine levels
- Hypomagnesemia: low magnesium levels
- Neutropenia: low neutrophil count
- Thrombocytopenia: low platelet count 2
From the Research
Abnormal Blood Tests in Medullary Thyroid Cancer
The following blood tests are abnormal in medullary thyroid cancer:
- Calcitonin levels: elevated in all patients with medullary thyroid cancer, and significantly more elevated when metastases are present 3, 4, 5
- Carcinoembryonic antigen (CEA) levels: high in most patients with medullary thyroid cancer, and more frequently elevated in patients with metastases 3, 6, 4
- Calcitonin doubling time: a strong prognostic indicator for medullary thyroid cancer recurrence and death, with shorter doubling times indicating progressive disease 3, 6
- CEA doubling time: also a strong prognostic indicator for medullary thyroid cancer recurrence and death, with shorter doubling times indicating progressive disease 3, 6
Diagnostic Value of Blood Tests
The diagnostic value of these blood tests is as follows:
- Basal calcitonin levels: helpful for the early detection of medullary thyroid cancer and for predicting lateral neck lymph node metastasis 5
- Calcium-stimulated calcitonin levels: did not improve preoperative diagnostics compared to basal calcitonin levels alone 5
- Combination of calcitonin and CEA levels: crucial to understand and interpret the various combinations of fluctuations in these levels within a clinical context to reduce diagnostic errors and improve patient outcomes 7
Prognostic Indicators
The following are prognostic indicators for medullary thyroid cancer: