The Extent of Thyroid Surgery in Differentiated Thyroid Cancer Patients with Low and Intermediate Risks of Recurrence

• Background:
  • Thyroid nodules and thyroid cancer are common clinical problems
  • The primary initial treatment of thyroid cancer is surgery:
    • Either thyroid lobectomy or total thyroidectomy
  • Experts have debated the extent of thyroid surgery and its impact on patient outcomes for many years
  • The 2015 ATA guidelines:
    • Endorsed thyroid lobectomy for low-risk differentiated thyroid cancers (DTCs):
      • Measuring 1 to 4 cm without extra-thyroidal extension (ETE) and clinical lymph node metastasis, in the absence of a family history of thyroid cancer and a personal history of radiation exposure to the head and neck
  • Subsequent literature has suggested that there has been a significant shift away from more extensive thyroid surgeries:
    • In managing benign and malignant thyroid disease
  • One study showed that the use of thyroid lobectomy in patients with thyroid cancer:
    • Increased from 17% in 2015 to 28% by the end of 2018
  • The current study was performed to further understand this surgical trend in patients with low-risk DTCs
• Methods:
  • This was a retrospective study of patients with well-differentiated thyroid cancer who underwent thyroid surgery at Memorial Sloan Kettering Cancer Center between 1986 and 2015
  • Patients were staged according to the American Joint Committee on Cancer 8th edition and classified as being at low, intermediate, or high risk for recurrence according to the 2015 ATA guidelines
  • The 2015 ATA dynamic risk-stratification system was used to assess the initial response to therapy within the first year
  • Patients with distant metastases; positive lymph nodes; stage T3, T4, or Tx; and ATA high risk of recurrence and who had undergone surgery other than total thyroidectomy (TT) or thyroid lobectomy (TL) were excluded
  • Propensity matching to create matched sets of TL and TT patients was used
  • Age, sex, histology, I-131 therapy, ATA risk, and pathologic T and N stage were used as propensity-matching criteria
  • Pearson’s test or Fisher’s exact test and the t-test were used to compare categorical and continuous variables, respectively
  • After propensity matching, multivariate analysis of the cohort using Cox proportional-hazards regression was performed
  • The primary outcomes were overall survival (OS), disease-specific survival (DSS), and recurrence-free survival (RFS)
  • The Kaplan–Meier method was used to compare the primary outcome, and a log-rank test was used to compare the two groups
• Results:
  • A total of 3756 patients were included in the initial cohort (943 TL and 2813 TT)
  • The cohort used for analysis was then restricted to 1836 patients (918 patients in each group after propensity matching)
  • There were no differences in age, sex, histology, T stage, and ATA risk classification
  • The mean follow-up periods for TL and TT patients were 56.34 and 56.85 months, respectively
  • When comparing TL with TT, overall survival (10-year OS, 92.2% vs. 91.3%; P = 0.967), disease-specific survival (10-year DSS, 100% vs. 99.1%; P = 0.197), and recurrence-free survival (10-year RFS, 99.5% vs. 98.3%; P = 0.079) were not significantly different
  • Multivariate analysis showed that between variables of age, vascular invasion, microscopic ETE, margins, and extent of surgery, only age greater than 55 years was a predictor of OS (HR, 5.773; P<0.0001)
  • There were 67 and 45 deaths in the TL and TT groups, respectively:
    • Only 1 death was related to thyroid cancer, and it was in the TT group
  • There were 15 patients with recurrence, 10 (1.08%) in the TT group and 5 (0.05%) in the TL group
  • The median times from surgery to recurrence were 44.2 and 44.1 months for the TL and TT groups, respectively
  • There was no statistical difference between the two groups regarding the site of recurrence
• Conclusions:
  • Thyroid lobectomy is associated with mortality outcomes similar to those for total thyroidectomy in selected DTC patients with ATA low and intermediate risk for recurrence
  • It is reasonable to consider lobectomy in patients with:
    • Intrathyroidal DTCs less than 4 cm, no nodules in the contralateral lobe, and no suspicious lymph nodes on either preoperative imaging or intraoperative palpation
• Thyroid lobectomy is associated with fewer complications such as hypoparathyroidism, recurrent laryngeal nerve injury, and hypothyroidism
• However, the extent of thyroid surgery remains the subject of debate between experts despite the reported excellent outcomes in patients with low-risk thyroid cancers <4 cm treated with thyroid lobectomy
• This study also supports findings from these other studies in examining the extent of thyroid surgery on the long-term mortality outcomes of patients with low-risk thyroid cancer
• Also included in this study were 402 patients with ATA intermediate risk of recurrence:
  • There were 212 total thyroidectomies and 190 thyroid lobectomies, and no significant differences were identified between the two groups regarding overall survival, disease-specific survival, and recurrence-free survival
  • Because intermediate-risk features on histology are identified only postoperatively, these patients would usually be advised to undergo completion thyroidectomy
  • The likelihood of requiring completion thyroidectomy based on intermediate-risk disease has been reported to be around 30% to 60%
  • However, it has not been proven that completion thyroidectomy has a survival advantage over thyroid lobectomy in all patients with an intermediate risk of recurrence
• A study of 341 patients with papillary thyroid cancer (PTC) and intermediate risk of recurrence showed no benefit of total thyroidectomy in recurrence-free survival and disease-specific survival, as compared with thyroid lobectomy
• Another study of 129 patients with unilateral micro-PTC and ipsilateral lateral lymph node metastases without gross ETE showed non statistically significant recurrence-free survival between the group of patients treated with thyroid lobectomy plus lymph node dissection and that treated with total thyroidectomy plus lymph node dissection, with 60 months of follow-up
• The current study also concludes that thyroid lobectomy has an outcome equivalent to that for total thyroidectomy in selected patients with intermediate risk of recurrence
• Additional studies and long-term follow-up are warranted to examine the extent of thyroid surgery in thyroid cancer patients with an intermediate risk of recurrence
• It is essential to remember that many of these studies were carried out in a tertiary care center with experienced sonographers and experienced thyroid surgeons
• This recommendation may not translate to institutions where there is lower surgical volume and where radiologists may have less expertise in identifying suspicious findings related to thyroid cancer
• Patients’ preferences and financial status and ability to attend follow-up visits are also essential factors to consider
• Thus, the findings of this study are reassuring to show that selected patients even in this latter group (intermediate risk DTC patients) have similar long-term outcomes after thyroid lobectomy
• References
  • Haugen BR, Alexander EK, Bible KC, Doherty GM, Mandel SJ, Nikiforov YE, et al. 2016 2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer: The American Thyroid Association guidelines task force on thyroid nodules and differentiated thyroid cancer. Thyroid 26:1–133.
  • Toumi A, DiGennaro C, Vahdat V, Jalali MS, Gazelle GS, Chhatwal J, Kelz RR, Lubitz CC 2021 Trends in thyroid surgery and guideline-concordant care in the United States, 2007-2018. Thyroid 31:941–949.
  • Matsuura D, Yuan A, Harries V, Shaha AR, Tuttle RM, Patel SG, Shah JP, Ganly I 2021 Surgical management of low-/intermediate-risk node negative thyroid cancer: A single-institution study using propensity matching analysis to compare thyroid lobectomy and total thyroidectomy. Thyroid 32:28-36.

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