Results
Of the 1019 consecutive patients who underwent thyroidectomy between January 1st 2006 and December 31st2015among whom 589 (95.4%) were diagnosed with WDTC. A total of 132 (22.4% of patients diagnosed with WDTC), met the inclusion criteria. The study group was comprised of 88 females (66.7%) and 44 males (33.3%), with a mean age of 53.4 ± 16.6 years (median 54.5 years, range 12-88; IQR [41-65]), and a mean follow-up of 39.9 ± 31.5 months (median 29.7 months, range 0-117.7 months; IQR [14.5-62.4]).
Twenty-seven patients (20.4%) had strap muscle invasion. This group was comprised of 21 females (77.7%) and 6 males (22.3%) with a mean age of 53.5 ±16.7 years (median 55, range 12-85 years; IQR [42-62]). The mean follow-up time was 27.1± 24.9 months (median 23.7 months, range 0-98.3 months; IQR [6.9-37.9]). The final pathological results revealed that 18 patients (66.7%) had an R0 resection, and that the remaining 9 patients (33.3%) had positive microscopic margins (R1). The baseline clinical and treatment details of the study cohort are listed in Table1.
Twenty-two patients (16.7%) had minimal tracheal invasion. This group was comprised of 16 females (72.7%) and 6 males (27.3%) with a mean age of 54 ±17.9 years (median 52, range 24-88 years; IQR [43-65.75]). The mean follow-up time was 54.4 ± 35.8 months (median 48.7 months, range 0-117.7 months; IQR [22.0-86.7]). The final pathological results revealed that 16 patients (72.7%) had an R0 resection, and that the remaining 6 patients (27.3%) had positive microscopic margins (R1). The baseline clinical and treatment details of the study cohort are listed in Table1.
Eighty-three patients (62.9%) had other forms of ETE (excluding minimal tracheal invasion). The other ETE group was comprised of 50 females (60.2%) and 33 males (39.8%) with a mean age of 53.3 ± 16.4 years (median 56 years; range: 17-83, IQR [41-66]). The mean follow-up time was 40.2 ± 30.9 months (median 29.6 months; range 0.1-109.9 IQR [13.8-63.6]). The final pathological results revealed that 60 patients (72.3%) had an R0 resection, and that the remaining 23 patients (27.7%) had positive microscopic margins (R1) (Table 1).
The statistical analysis did not reveal any significant differences between the minimal tracheal ETE group, strap muscle, and the non-tracheal ETE group in patient’s age, extent of surgery, or length of follow-up (Table 1). The final pathological analysis did not reveal any significant difference (p= 0.84) in R1 results between the non-tracheal ETE group (n =23; 27.7%) and the minimal tracheal ETE group (n =6; 27.3%) and strap muscle group (n=9, 33.3%). All other pathological parameters, including lymph node involvement, multifocal disease, and perivascular and perineural invasion were not significant different between the tracheal and non-tracheal ETE groups (Table 1).
Postoperative RAI treatment was delivered to 15/22 patients (68.2%) in the minimal tracheal ETE group (average dose 118.81 ± 107.60 mCi) , 15/27(55.6%, avarage dose of 78.13 ± 73.85) in the t3b (strap muscle involvement, and 55/81 patients (67.9%) in the non-tracheal t4a ETE group (average dose 140.77 ± 154.36 mCi) (p= NS) (Table 1). Six patients (6/81) in the \souttracheal gr non-tracheal t4a ETE group underwent radiation therapy (p= NS) (Table 1), no patients underwent EBRT in the two other groups. Recurrence was diagnosed in two patients (2/27) in the strap muscle (t3b) group; 16/78 (20.5%) in the T4a other tracheal invation group, and one patient (1/22) (4.5%) in the minimal tracheal invasion group (p= NS). (Table 1)
Kaplan-Meier models that analyzed the difference in DFS (structural recurrence) between T3b ETE disease (strap muscle involvement) to T4a shave and T4a other ETE (other structural disease) did not yield any significant differences for the overall population (all ages) between the tracheal invasion group and the other forms of ETE (p= 0.084; Fig. 1A, Table 1).
One subgroup analysis of patients >55 years of age that compared structural recurrence (DFS) in T3b ETE disease (strap muscle involvement) to T4a shave and other T4a (RLN, larynx, esophagus, subcutaneous tissue) also did not reach a level of significance, but there was a strong trend towards significance (p= 0.064; Fig. 1B, Table 2).
Another subgroup analysis that involved combining T3b patients with T4a shave patients and comparing them to other T4a ETE patients (RLN, larynx, esophagus, subcutaneous tissue) revealed that the former performed significantly better than the latter [p= 0.028 for all ages; p= 0.021; for patients >55 years of age (Fig.1 C and D, respectively; Tables 3 and 4] in terms of structural recurrence (DFS).