Gross Extrathyroidal Extension into Strap Muscles and Disease-Specific Mortality in Papillary Thyroid Cance

• Clin Thyroidol 2022;34:78–80.
• Background:
  • Several studies have reported that microscopic extrathyroidal extension (m-ETE) does not increase disease-related mortality in patients with papillary thyroid cancer (PTC); however, the literature is scarce with regard to the impact of macroscopic (gross) extrathyroidal extension invading only strap muscles (T3b-ETE) on outcomes that are important to patients
  • This study was performed to evaluate the association between T3b-ETE tumors and disease-specific survival (DSS) in patients with PTC
• Methods:
  • This hospital-based single-institution study included adults who underwent initial surgery for PTC, with or without local or distant metastasis, between 1986 and 2015
  • The cohort was classified into three groups:
    • Mo macro-ETE:
      • No gross intra-operative evidence of extrathyroidal extension
    • T3b-ETE:
      • Gross intraoperative evidence of extra-thyroidal extension invading only strap muscles
    • T4-ETE:
      • Gross intraoperative evidence of extrathyroidal extension invading subcutaneous soft tissues, larynx, trachea, esophagus, recurrent laryngeal nerve, prevertebral fascia, or carotid artery/mediastinal vessels
  • A Cox proportional-hazards model was used to investigate the association of ETE categories and 10-year disease-specific survival (DSS, defined as the interval between initial surgery and last appointment or death with evidence of local or distant disease)
  • This model was adjusted for pathologic nodal stage, distant metastasis stage, and age
  • A subgroup analysis by age (< 55 vs. ≥ 55 years) was planned
• Results:
  • A total of 5880 patients with a median follow-up of 64 months were included
  • Most were female (72.2%), were < 55 years of age (68.2%); had a tumor size between 0 and 4 cm (94.6%); were classified as T1 (71.3%), N0/Nx (68.1%), and M0 (98.9%); had ATA intermediate-risk disease (37.6%); and had AJCC stage I disease (89.4%)
  • Overall, 5485 patients had macro-ETE (93.3%), 179 had T3b-ETE (3.0%), and 216 had T4-ETE (3.7%)
  • In the overall adjusted multivariate analysis and compared with the no macro-ETE group, the T3b-ETE group had a similar risk of DSS (HR, 2.11; 95% CI, 0.72–6.15) and the T4-ETE group had a higher risk of DSS (HR, 5.22; 95% CI, 2.90–9.40)
  • In the subgroup analysis, patients ≥ 55 years of age with T3b-ETE had a higher risk of DSS as compared with patients with no macro-ETE (HR, 3.29; 95% CI, 1.07–10.08), similar to the higher risk also seen in the T4-ETE group (HR, 9.39; 95% CI, 4.68–18.81)
  • There were 26 patients with residual disease after initial surgery (none from the T3b-ETE group), and there were only 60 DSS events
• Conclusions:
  • Macroscopic extrathyroidal extension invading only the strap muscles (T3b-ETE) increases disease-specific death in patients with PTC who are ≥55 years of age, as compared with patients with no macro-ET
• This retrospective study found no increased disease-specific mortality in patients with T3b-ETE overall and increased disease-specific mortality only in those ≥55 years
• The strength of the Harries et al. study is the meticulous record review and histologic confirmation of the intraoperative T3b-ETE findings
• Nevertheless, the small number of DDS events limited the analysis of other prognostic factors in the multivariate model, including the tumor size and impact of postoperative radioactive iodine ablation
• The literature about the impact of extrathyroidal extension (ETE) on disease outcomes provides inconsistent conclusions
• Factors contributing to different findings are the lack of a standard definition and reporting of ETE
• For instance, some studies defined ETE and its severity by the direction of invasion (perithyroid tissue, strap muscle, and beyond strap muscle), while others defined ETE based on pathology reports and operative findings
• Therefore, it is expected that different definitions of the disease may lead to different outcomes and conclusions
• Macroscopic ETE is defined as an operative or gross examination finding noted when cancer extends out of the thyroid into adjacent structures
• In contrast, microscopic ETE is defined as when the tumor invasion is observed under a microscope
• It is expected that all macroscopic ETE will have evidence of microscopic ETE
• These definitions imply that clinicians taking care of patients with thyroid cancer should carefully review the pathological report and the operative report to classify ETE correctly
• We have also found that frequent communication with our surgical colleagues can help clarify the operative and histopathologic findings
• Future studies using standardized definitions will elucidate the impact of macroscopic disease on recurrence and mortality in PTC
• In the meantime, we agree with the authors of this study that it is prudent to consider T3b-ETE as a prognostic adverse risk factor between microscopic ETE and macroscopic ETE with invasion into adjacent tissues

#Arrangoiz #ThyroidSurgeon #ThyroidExpert #HeadandNeckSurgeon #CancerSurgeon #PapillaryThyroidCancer #ExtrathyroidExtension #Miami #Mexico #MountSinai #EndocrineSurgery #SurgicalOncology #Surgeon #Teacher