Thyroid cancer incidence is increasing worldwide. Though long-term survival rates are excellent, recurrence remains a significant problem, which highlights potential areas of needed improvement, including the surgical care of these patients. This review paper identifies tools and markers that can be used to improve surgical quality in thyroid cancer. Preoperative surgical planning starts with an adequate ultrasound evaluation of the cervical lymph node basins. Postoperatively, thyroglobulin and radioactive iodine uptake scans can track adequacy of resection. In addition, lymph node yield and lymph node ratios serve as indirect markers for assessing the quality of lymph node dissections. Current research also suggests that high-volume surgeons have improved oncological outcomes. Surgeons can use these tools and information to follow and potentially improve the care provided to patients.
Thyroid cancer, surgical quality, ultrasound, thyroglobulin, nodal dissection
Disclosure: Maria F Bates, Kristin L Long, and Rebecca S Sippel have nothing to declare in relation to this article. No funding was received in the publication of this article. This study involves a review of the literature and did not involve any studies with human or animal subjects performed by any of the authors.
Authorship: All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship of this manuscript, take responsibility for the integrity of the work as a whole, and have given final approval to the version to be published.
This article is published under the Creative Commons Attribution Noncommercial License, which permits any noncommercial use, distribution, adaptation, and reproduction provided the original author(s) and source are given appropriate credit.
February 21, 2017 Accepted
April 24, 2017
Maria F Bates, Department of Surgery, 600 Highland Avenue, K4/739 CSC, Madison, WI 53792, US. E: firstname.lastname@example.org
Thyroid carcinoma is one of the most common solid tumors worldwide. The incidence of thyroid cancer is increasing, with an estimated 57,000 newly diagnosed cases in the US in 2017. Approximately three-quarters of these patients are female, with the majority being between 20 and 34 years of age. Though five-year survival rates are greater than 98% overall, the disease still inflicts significant morbidity on those affected.1 At present, surgery represents the mainstay for treatment and the only option for a definitive cure. Performing the appropriate operation for thyroid carcinoma is the first step towards achieving optimal outcomes. Current quality markers in thyroid surgery are predominately based on morbidity from often transient complications, such as temporary hypoparathyroidism or recurrent laryngeal nerve palsy. In order to improve the surgical care of patients with thyroid cancer, it is important that we focus not just on safety, but also on oncologic outcomes. Given the time delay to disease recurrence, surgeons are often not aware that disease recurrence has been identified or that the recurrence may have been due to inadequate initial surgical management. In a recent retrospective view of our institutional data, we collected all patients that underwent re-operative surgery for differentiated thyroid cancer. We found that the majority of patients had abnormal radiographic and/or elevated thyroglobulin (Tg) levels at their 6 month postoperative follow up from their initial surgery. Only three patients out of 92 actually had a negative ultrasound and undetectable Tg within 1 year, defining them as truly recurrent disease. By this definition, the remaining patients really just underwent a re-operation for persistent disease, which suggests a need for improved surgical quality. In order to improve the quality of thyroid cancer surgery, we need to identify short-term markers that can be used to give feedback to surgeons to allow them to improve their surgical care. In this review, we focus on the importance on quality surgery for thyroid cancer, specifically on the initial pre-operative evaluation, surgeon volume and outcomes, adequacy of surgical resection, and nodal disease. It is our hope that surgeons who perform surgery for thyroid cancer will use this information not only to track their own clinical outcomes but also to use these tools to re-evaluate the quality of care given to their patients.
Quality surgery starts with a good pre-operative evaluation
In order to achieve curative surgery as well as optimizing the effects of postoperative treatment and
facilitate follow-up, surgeons must eradicate all the disease from the neck at the initial operation.
Pre-operative radiographic imaging is the first step towards optimizing these outcomes. The neck
ultrasound has emerged as the recommended first-line imaging modality to evaluate, not only disease
within the thyroid gland, but also any potential spread to the central or lateral nodal basins in the neck.
The most recent American Thyroid Association (ATA) guidelines recommend a formal pre-operative
neck ultrasound evaluation of nodal disease prior to undergoing any thyroid surgery.2,3 This is further
supported by Kocharyan and colleagues who demonstrated that lymph node disease identified on
pre-operative ultrasound accurately corresponds to postoperative lymph node pathology.4
Pre-operative ultrasound evaluation primarily determines the extent of surgery performed and assists in determining prognosis. The quality of ultrasound exams of the neck is very operator-dependent and there is significant variability in interpretation of this modality. One recent study focused on the implementation of pre-operative ultrasound evaluation of lymph node disease in patients with well-differentiated thyroid carcinoma. This study demonstrated that high-quality cervical ultrasound changed the operative approach in 23% of patients, where a majority underwent more extensive operations for otherwise clinically occult lymph node metastases.5 Unfortunately, not all ultrasounds are equal and significant variability exists between non-specialist performed neck ultrasounds and specialist-performed neck ultrasounds. Mazzaglia evaluated 261 patients treated by a single surgeon for management of their thyroid disease over a two-year period, all of whom had an outside neck ultrasound available for comparison. Surgeon performed ultrasound (SPUS) was conducted on all patients by one surgeon, and 18% of the cohort had a change in treatment plans due to ultrasound discrepancies between the outside ultrasound and the SPUS. In eight of 132 patients undergoing thyroidectomy, the operative plan was significantly altered based on the results of the SPUS.6 Similar studies have also noted the superiority of the surgeon-performed ultrasound.7
At our institution, we compared outcomes for thyroid cancer patients with pre-operative ultrasounds performed by a thyroid specialist versus a non-specialist. We demonstrated that a thyroid specialist was much more likely to document lymph status (69 versus 20%).8 In addition, patients with a pre-operative ultrasound performed by a specialist had lower uptake on postoperative radioactive iodine scans and lower recurrence rates compared to those who had an ultrasound performed by a nonspecialist. In those patients with a pre-operative ultrasound performed by a non-specialist, a significant number of recurrences arose less than 12 months after their initial surgery. These early recurrences are likely secondary to inadequate initial surgery due to poor pre-operative recognition of the extent of disease.8 These findings prompted radiologists to re-evaluate their techniques and create a standardized approach to neck ultrasound for thyroid cancer that incorporates the ATA guidelines as well as focuses specific attention to the pertinent questions for endocrine surgeons.9 In summary, any patient undergoing thyroid surgery should have a thorough evaluation of the cervical lymph node basins prior to surgery. In addition, it is important to consider the experience of the proceduralist performing the ultrasound and his or her familiarity with cervical neck ultrasound for thyroid carcinoma.
Abnormal lymph node features on ultrasound include larger size, loss of fatty hilum, round rather than oval shape, hyper-echogenicity, cystic changes, micro-calcifications, and peripheral vascularity. Of these variables, studies have demonstrated that peripheral vascularity and micro-calcifications show the highest sensitivity and specificity for detecting metastatic disease.10,11 Once identified by ultrasound or physical exam, abnormal lymph nodes in the lateral neck should undergo cytological confirmation with fine needle aspiration (FNA) in order to determine the extent of dissection needed. When cytology is inadequate or ultrasound and cytology findings are discordant, Tg washout testing can be done to confirm the presence of metastatic disease.12,13 Pre-operative FNA is not always necessary to evaluate central neck lymph nodes. These nodes can be difficult to access with FNA when the thyroid is in situ and can be easily assessed during the thyroid operation. It is best to perform a central lymph node dissection concomitant to thyroid surgery as the procedures utilize the same incision. Therefore, if there are concerning findings on pre-operative ultrasound within the central neck, a central neck dissection during the initial operation best serves the patient.
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Thyroid cancer, surgical quality, ultrasound, thyroglobulin, nodal dissection