Well-differentiated thyroid cancer (WDTC) includes papillary, follicular, and Hurthle cell cancer. Surgery for thyroid cancer is an important element of a multifaceted treatment approach. Extent of thyroidectomy has always been a debatable topic. According to previous American Thyroid Association (ATA) guidelines 1 published in 2009, total thyroidectomy (TT) was endorsed as a surgical treatment option for all differentiated thyroid cancers >1 cm. However, multiple studies demonstrated that, in properly selected patients, results even after thyroid lobectomy (TL) were very similar to TT outcome. Accordingly, ATA made significant changes in 2015 guidelines. 2 For patients with thyroid cancer <1 cm TL and for patients with cancer >4 cm TT are the recommended options. There is not much controversy as there is only one recommended a surgical option. However, for patients with thyroid cancer >1 cm and <4 cm, the treatment team has option to choose between TL and TT. Clinicians often find it difficult to decide between lobectomy and TT. The purpose of this review article is to evaluate available literature to apprise professionals and patients of the best available evidence regarding the extent of thyroidectomy.
Proponents of TT for WDTC argue that complete resection of thyroid tissue affords the opportunity to use radioactive iodine (RAI) for postoperative detection of residual or metastatic disease, as well as for treatment, and it facilitates the use of serum thyroglobulin as a marker to detect residual disease and recurrence. 3 , 4 TT, additionally, has the advantage that it can eliminate undetected multifocal disease in the contralateral lobe. 5 On the other hand, those who advocate for TL emphasize that WDTC is an indolent disease with an excellent prognosis; patients should not be subjected to higher risks for TT-related complications such as hypoparathyroidism and recurrent laryngeal nerve injury without a clear survival benefit. 6 In addition, in 50%–75% of patients, the presence of the remaining lobe of the gland may obviate the lifelong need for exogenous thyroid hormone therapy. 7
In an analysis of 52,173 papillary thyroid cancer (PTC) patients, Bilimoria et al. demonstrated a slightly higher 10-year relative overall survival for TT as opposed to TL (98.4% vs. 97.1%, respectively, P < 0.05) and a slightly lower 10-year recurrence rate (7.7% vs. 9.8%, respectively, P = 0.05). 8 However, data on extrathyroidal extension, completeness of resection, and other comorbid conditions, which could have had a major impact on survival and recurrence risk, were not available. No information on specific high-risk histological subtypes of papillary carcinoma was included, and recurrence data were reported as locoregional, rather than separating local from nodal recurrence. Adam et al. performed an updated analysis of 61,775 patients in the National Cancer Database who underwent thyroid surgery between 1998 and 2006. 9 They demonstrated that the overall survival advantage seen for patients with 1–4 cm PTC who underwent thyroidectomy in the study by Bilimoria et al. disappeared when further adjustment was made for additional variables related to complexity and severity of illness. This lack of overall survival advantage was also seen when the group was subdivided into patients with 1–2 cm and 2–4 cm PTC. In contrast to the Bilimoria results, Haigh et al. used the additional data recorded in the SEER database to show that TT did not confer a survival advantage in either low- or high-risk groups using the age, metastases, extent, and size risk-group classification. 10
A similar multivariate analysis of the SEER database by Mendelsohn et al. controlling for tumor size in a cohort of over 20,000 patients found no survival difference in patients who underwent TT in comparison to TL. 11 Davies and Welch reported similar results in an analysis of 35,000 patients managed between 1973 and 2005, again finding no advantage after TT. 12 The National Thyroid Cancer Treatment Cooperative Study Group from North America reported on almost 3000 patients in 2006 and was unable to show an improved disease-specific survival or disease-free survival at any stage of disease based on the extent of surgery. 13
Recently, Barney et al. analyzed the SEER database and included 23,605 differentiated thyroid cancer patients diagnosed between 1983 and 2002 (12,598 TT and 3,266 lobectomy). They found no difference in 10-year overall survival (90.4% for TT vs. 90.8% for lobectomy) or 10-year cause-specific survival (96.8% for TT vs. 98.6% for lobectomy). Furthermore, in a multivariate analysis that included age, tumor, node, metastasis, sex, year of diagnosis, extent of surgery, and RAI use, no difference in overall survival or cause-specific survival was seen with respect to the extent of initial surgery. 14
Consistent with the SEER data analyses, two single-center studies also confirm that lobectomy is associated with excellent survival in properly selected patients. After a median follow-up of 8 years, only one disease-specific death was seen in a cohort of 889 PTC patients with T1-T2 tumors treated with either TT (n = 528) or lobectomy (n = 361) at Memorial Sloan Kettering Cancer Center, New York. 15 In this study, out of 361 patients treated with initial lobectomy only, 14 patients (4%) required a completion thyroidectomy at a later date; seven patients (2%) developed a malignancy of the same histological subtype in the contralateral lobe, two patients (0.7%) developed a malignancy of different histological subtypes in the contralateral lobe, and further five patients (1.3%) had the contralateral lobe removed for benign nodules. Therefore, only nine patients (2.7%) developed a malignancy in the contralateral lobe. Hence, it was concluded that this low figure is good evidence to justify the policy of lobectomy adopted in these patients.
Furthermore, Matsuzu et al. reported a cause-specific survival rate of 98% after a median of 17 years of follow-up in properly select PTC patients treated with lobectomy and ipsilateral neck dissection. 16 Kim et al. examined the association between the extent of surgery and tumor size on recurrence and survival in 1041 PTC patients with tumors 4 cm or less. 17 This study showed no significant difference in posttreatment recurrence between TT and lobectomy PTC patients. To avoid selection bias, they adopted a risk stratification approach according to known adverse features, but whether a TT improved the survival and recurrence outcomes more than TL was uncertain.
However, in contrast, there are other studies which have reported poorer outcome when patients are treated with TL. For example, Loh et al. reviewed their experience of 700 patients treated at their institution over a 25-year period. They found that lobectomy or sub-TT resulted in increased rates of both recurrence and death compared with near-total or TT. This analysis, however, included patients treated for recurrence, when treated primarily outside their institution, making interpretation of exact surgical details less accurate. They excluded patients treated with T1N0M0 disease, who constitute a large part of group who would undergo TL. 18 Mazaferri et al. reviewed the outcomes of over 1000 patients treated at multiple institutions and found improved recurrence and survival rates in patients who underwent more extensive surgery. This effect was found to have an independent effect on survival on multivariate analysis. This group also chose to exclude patients with lesions under 1.5 cm from the analysis. 19
In a comparative analysis from Japan, outcomes between TL and TT in 173 patients with PTC, 1–5 cm tumor using propensity score matching, were assessed. 20 Equivalent prognoses were observed for patients treated with TL and TT in this study. Furthermore, TL was associated with fewer adverse events than TT.
Debate over the extent of thyroid surgery for WDTC relates in part to complications of TT versus lobectomy. Rates of complication for thyroid surgery are significant. A study of 5583 thyroid cases operated in the USA in 1996 for WDTC reported a postoperative hypocalcaemia rate of 10% and a recurrent laryngeal nerve palsy rate of around 1%. 21 Multicenter studies from Italy and Scandinavia reported very similar findings. 22 , 23 A study based on the Nationwide Inpatient Sample of surgeries performed in the USA, 1999–2003, reported significantly higher rates of hypocalcemia (10.6% vs. 3.5%), unilateral vocal cord palsy (1.1% vs. 0.6%), and bilateral vocal cord palsy (0.4% vs. 0.1%) following TT rather than TL performed for malignancy. 24 An Italian study of 14,934 patients from 42 experienced endocrine surgery units reported symptomatic hypocalcemia rates of 14% following TT compared with 0.4% following TL.
They went on to report higher rates of both unilateral and bilateral recurrent laryngeal nerve palsy, tracheotomy, hemorrhage, and wound infection in the group treated with TT. 22 However, experts in thyroid surgery report low rates of complications following both lobectomy and TT. 25 Because recent data convincingly supported limited thyroid resection as an equivalent strategy in properly selected patients, the 2015 ATA guidelines adopted a risk-based management strategy that considers TL as a treatment option for select tumors larger than 1 cm and no larger than 4 cm. 2 A selective approach to RAI ablation has become favored in low-risk patients; therefore, the use of TT specifically as preparation for RAI administration in treatment or follow-up has become a less important rationale. 7 Therefore, if a patient is considered to have equivalent long-term disease outcomes with TL and without RAI treatment or suppression therapy, that patient would be best served by limiting the aggressiveness of treatment, minimizing adverse events, and maximizing the quality of life. It is very important to have an informed discussion with the patient about the options of TL versus TT. If the thyroid mass is a single nodule <4 cm with no contralateral nodules in the opposite lobe and without evidence of extrathyroidal extension, patients should be given the option of TL. TT should be performed if the contralateral lobe also harbors a nodule, or if patients have clinically significant lymph node metastasis, gross extrathyroidal extension, evidence of distant metastasis and if the treatment strategy is to include postoperative RAI imaging or therapy.
In conclusion, patients are best served by working with a multidisciplinary team that can coordinate and personalize this decision-making before the initial surgical treatment plan. 26 In properly selected low-to-intermediate risk patients, the extent of initial thyroid surgery has little impact on disease-specific survival.
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Conflicts of interest
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