Thyroid cancer molecular testing

New state of the art molecular testing is promising to reduce un-necessary surgeries for thyroid cancer. Traditionally, thyroid nodules or lumps in the thyroid gland were tested using fine needle aspiration biopsy under ultrasound guidance. With this technique, a thin needle is inserted under precision guidance into the thyroid nodule and cells within the nodule area aspirated and examined under the microscope to make a diagnosis. Decision to operate on the thyroid gland to remove possible malignancy is heavily based on this diagnostic study. Unfortunately in many cases, the results of the traditional biopsy result falls in the grey area.

 

Table 2

Diagnostic category Risk of malignancy (%) Usual management
Nondiagnostic or unsatisfactory 1–4 Repeat FNA with ultrasound guidance
Benign 0–3 Clinical follow-up
Atypia of undetermined significance or follicular lesion of undetermined significance 5–15 Repeat FNA
Follicular neoplasm or suspicious for follicular neoplasm 15–30 Surgical lobectomy
Suspicious for malignancy 60–75 Near-total thyroidectomy or surgical lobectomy
Malignant 97–99 Near-total thyroidectomy

 

Source: Indian J Otolaryngol Head Neck Surg. 2012 Dec; 64(4): 305–311.

 

As you can see in the chart above other than the clearly defined “benign” and “malignant” categories, there are several categories with unclear diagnostic implications with cancer rates ranging from 5 to 75%. In the past the rule of thumb was to suggest either surgery or close observation with repeat fine needle aspiration and in majority of my patients, the decision was to proceed with surgery.

Molecular testing today allows further analysis of samples to look for changes in DNA/RNA of the cells to further narrow the likelihood of cancer in some of those uncertain categories. Although it does not rule in or rule out cancer 100% of the time, it certainly offers the potential of avoiding unnecessary surgery in many cases. The cost of the technology which in the past may have been into the thousands, has declined significantly with automation these days and it is widely available from various companies (ThyGenX, AFIRMA, ThyroSeq) and covered by many insurances with relatively low out of pocket costs. So before undergoing thyroid surgery, ask your surgeon if molecular surgery would benefit you.

July 3rd, 2017 by