Can We Predict the Presence of Central Neck Nodal Metastasis in Patients with Papillary Thyroid Cancer?
Thompson AM, Turner RM, Hayen A, Aniss A, Jalaty S, Learoyd DL, Sidhu S, Delbridge L, Yeh MW, Clifton-Bligh R, Sywak M. A pre-operative nomogram for the prediction of ipsilateral central compartment lymph node metastases in papillary thyroid cancer. Thyroid. October 1, 2013 [Epub ahead of print].
SUMMARY • • • • • • • • • • • • • • • • • • • • • • • •
Papillary thyroid cancer (PTC) has a high rate of central nodal metastasis at the time of diagnosis. Surgical series report an incidence of central nodal metastases of 20% to 80%. A therapeutic central neck dissection is appropriate when there is clinical suspicion or pathologic confirmation of central neck nodal metastasis. Because central nodal metastases may be difficult or impossible to detect by sonographic, radiologic, or clinical means, a method to predict the status of the central compartment using preoperative clinical characteristics may be valuable.
Retrospective analysis of a database made up of prospectively collected data from a single institution was performed. A total of 1589 subjects who underwent an index operation for PTC between 1968 and 2012 were identified. Of these, 914 patients were identified who underwent a total thyroidectomy and removal of central neck nodes (either selectively or prophylactically). In 84% of cases the nodes were ipsilateral only. Clinical factors and tumor features were evaluated for their ability to predict the nodal status of the central compartment through a linear regression model. Internal and external validation of the data set was performed.
The rate of central nodal metastases was 43%. The mean maximum tumor diameter was 17.4 mm. Age, sex, tumor size, and multifocality were associated with central nodal status. Young and old age were associated with nodal metastasis (U-shaped curve). Men were 2.3 times more likely to have nodal metastases than women. Tumor size had a linear positive relationship to central nodal metastases; the rate was 60% for cancers greater than 5 cm.
Because prophylactic central neck dissection may increase the risk of surgical complications in exchange for marginal benefits in recurrence, and because radiologic studies and physical exam do not detect the presence of central neck nodal metastases well, there is benefit in preoperative risk stratification to guide decisions on how to manage the central compartment. Data from this study were used to create a nomogram that predicts the presence of central nodal metastases. A smart phone application was developed for the distribution of this nomogram.
ANALYSIS AND COMMENTARY • • • • • •
There is considerable controversy regarding the role of prophylactic central neck dissection in PTC. Some experts believe that prophylactic nodal dissection will reduce the central compartment recurrence rate and therefore they perform it routinely. Many reports have attempted to weigh the risks of prophylactic central neck dissection (specifically an increased risk of recurrent laryngeal-nerve injury and hypoparathyroidism) with the benefits of the reduction of central compartment metastases. Reoperative central neck dissection is believed to be more risky than a central neck dissection performed during the index operation for thyroid cancer. For all of these reasons, the limitation of central neck dissection to cases in which the probability of nodal metastases is highest is a meritorious goal. The criticisms of this study are that the authors did not discriminate between macroscopic and microscopic nodal metastases, which are believed to portend different clinical risks. In addition, the preoperative sonographic detection of multifocality may not be possible in many cases. The sonographic evaluation of the thyroid focuses on the dominant or most suspicious lesions in the thyroid and may fail to describe smaller, less clinically relevant lesions. If the application of this nomogram could reduce the probability of missing clinically significant nodal metastases and limit the number of patients who have to face the added risks of central neck dissection (including revisional central neck dissection), then it will prove to be useful in clinical practice. A number of other nomograms exist to aid the thyroid surgeon, including those that predict postoperative hypocalcemia (1), predict the need for performing FNA of a thyroid nodule (2), predict malignancy in thyroid nodules (3), and predict the probability of death from thyroid cancer (4). All nomograms should be used as a supplement to clinical knowledge and not as a substitute for clinical judgment or common sense.
- Ali S, Yu C, Palmer FL, Ganly I, Shaha A, Shah JP, Kattan MW, Patel SG. Nomogram to aid selection of patients for short-stay thyroidectomy based on risk of postoperative hypocalcemia. Arch Otolaryngo Head Neck Surg 2011;137:1154-60.
- Nixon IJ, Ganly I, Hann LE, Yu C, Palmer FL, Whitcher MM, Shah JP, Shaha A, Kattan MW, Patel SG. Nomogram for selecting thyroid nodules for ultrasound-guided fine-needle aspiration biopsy based on a quantification of risk of malignancy. Head Neck 2013;35:1022-5.
- Nixon IJ, Ganly I, Hann LE, Lin O, Yu C, Brandt S, Shah JP, Shaha A, Kattan MW, Patel SG. Nomogram for predicting malignancy in thyroid nodules using clinical, biochemical, ultrasonographic, and cytologic features. Surgery 2010;148:1120-8.
- Yang L, Shen W, Sakamoto N. Population-based study evaluating and predicting the probability of death resulting from thyroid cancer and other causes among patients with thyroid cancer. J Clin Oncol 2013;31:468-74.
CLINICAL THYROIDOLOGY • DECEMBER 2013 VOLUME 25 • ISSUE 12 • © 2013