From the Guidelines
Abnormal blood work in thyroid cancer should be evaluated with thyroid function tests and tumor markers, including TSH, free T4, free T3, thyroglobulin, and calcitonin, to guide treatment decisions and monitor for cancer recurrence. The most recent and highest quality study, 1, emphasizes the importance of imaging in diagnosing and characterizing thyroid findings for management. For patients with thyroid cancer, TSH levels are often kept suppressed (below normal range) using levothyroxine medication, typically at doses between 1.6-2.2 mcg/kg/day, to prevent cancer growth stimulation, as recommended by 1.
Key Blood Tests
- Thyroid stimulating hormone (TSH)
- Free T4
- Free T3
- Thyroglobulin (Tg)
- Calcitonin
Tumor Markers
- Thyroglobulin serves as a tumor marker for papillary and follicular thyroid cancers and should be undetectable after complete thyroid removal and radioactive iodine treatment, as stated in 1.
- Rising thyroglobulin levels may indicate cancer recurrence.
- For medullary thyroid cancer, calcitonin and carcinoembryonic antigen (CEA) are the relevant tumor markers.
Monitoring and Follow-up
Regular blood monitoring is essential, typically every 3-6 months initially, then annually if stable, as suggested by 1. Calcium levels should also be checked as thyroid surgery can affect parathyroid function. These blood tests help guide treatment decisions and monitor for cancer recurrence, making them crucial for proper thyroid cancer management.
Treatment Decisions
Treatment decisions should be based on the type of cancer, stage of disease, and patient's overall health, as outlined in 1. For example, papillary and follicular carcinomas are treated primarily with surgery and may have radioiodine ablation depending on the stage of disease. Medullary thyroid carcinoma is more aggressive and is treated with surgery. Anaplastic carcinoma is an aggressive undifferentiated tumor with a poor prognosis, and treatment does not significantly impact survival.
Imaging and Surveillance
Imaging plays a crucial role in operative planning, routine tumor surveillance, and further evaluation of suspected recurrence, as emphasized in 1. Imaging also plays a role in evaluation of non-neoplastic disease entities, such as goiter and thyrotoxicosis. The American College of Radiology (ACR) has published guidance regarding the incidental thyroid nodule detected on imaging, and ACR TI-RADS was conceived to aid management of thyroid nodules detected on ultrasound.
In summary, abnormal blood work in thyroid cancer requires a comprehensive evaluation with thyroid function tests and tumor markers, regular monitoring, and imaging to guide treatment decisions and monitor for cancer recurrence, as supported by the highest quality study, 1.
From the Research
Thyroid Cancer and Abnormal Blood Work
- Thyroid cancer is a common clinical problem, with approximately 43,720 new cases expected to be diagnosed in 2023 in the US 2.
- The 5-year relative survival rate for thyroid cancer is approximately 98.5% 2.
- Most cases of well-differentiated thyroid cancer are asymptomatic and detected during physical examination or incidentally found on diagnostic imaging studies 2.
- Abnormal blood work may indicate the presence of thyroid cancer, and further testing such as fine-needle aspiration biopsy and molecular markers may be necessary for diagnosis 3.
- The management of differentiated thyroid cancer (DTC) has undergone a paradigm shift toward the use of risk stratification, with the goal of maximizing the benefit and minimizing the morbidity of radioiodine (131I) therapy 4.
- Thyroglobulin levels and postoperative diagnostic radioiodine scintigraphy are used to guide 131I therapy and monitor for recurrent disease 4.
Diagnosis and Management
- The diagnosis of thyroid cancer typically involves a combination of clinical evaluation, imaging studies, and laboratory tests, including fine-needle aspiration biopsy and molecular markers 3.
- The management of thyroid cancer depends on the type and stage of the disease, as well as the patient's overall health and risk factors 2, 4, 3.
- Surgical resection is the preferred approach for patients with recurrent locoregional disease, while metastatic disease may be treated with surgical resection, stereotactic body irradiation, or systemic therapy 2.
- Targeted therapies such as dabrafenib and selpercatinib are directed to genetic mutations that give rise to thyroid cancer and are used in patients with advanced thyroid carcinoma 2.