Significance of microscopic cancer involvement to surgical resection margin in differentiated papillary thyroid cancer

Objectives In America Thyroid Association guideline for thyroid cancer, patients have incomplete tumor resection are classified into high risk group. However, relationship between microscopic residual tumor and recurrence has not been well elucidated. The aim of this study is to evaluate the relationship between microscopic cancerous surgical margin involvement and recurrence in differentiated papillary thyroid cancer (DTC) patients.

Methods Between Feb 2002 and Aug 2003, 197 DTC patients (184 women; mean age, 44.9 ±13.4 y) who received total thyroidectomy without gross residual tumor followed by high-dose radioiodine ablation (HDRIA) were reviewed. TSH stimulated thyroglobulin, neck ultrasonography, diagnostic radioiodine whole body scans, and F-18 FDG PET/CT were checked for recurrence detection. Diagnosis of the recurrence was based on histopathologic confirmation or clinical follow up. Cancer lesions found within 12 months after HDRIA were considered as a persistent disease instead of recurrence.

Results The mean follow-up from the HDRIA was 85.9 months.Twelve patients (6.1%) had microscopic cancerous margin involvement (margin (+) group), and 185 patients showed negative surgical resection (margin (-) group). One patient (8.3%) of margin (+) group and 28 patients (15.1%) of margin (-) group experienced tumor recurrence. Three patients (25.0%) of margin (+) group and 11 patients (5.9%) of margin (-) group had persistent disease. There was different rate of persistent disease (p<0.01), but no difference of recurrence rates between margin (+) and margin (-) groups. There were no significant differences in ablation success rates and disease free survival between the two groups.

Conclusions Although Margin (+) group had higher incidence of persistent disease, but there was no difference of recurrence rate. These results support that additional treatments are not necessary in DTC patients with cancerous surgical margin involvement after HDRIA