Endocrine Abstracts

Introduction: In recent years the growing rate of newly diagnosed papillary tyroid cancers (PTC) has been observed. Nowadays most of PTC are small (mostly <2cm in diameter) with no unfavourable patomorphological features, although the cases of incompletely resected PTC can still be encountered. Incomplete tumour resection, regardless of the presence of microscopic (R1) or macroscopic (R2) disease, after operation, is considered as a high-risk factor for PTC recurrence/persistent disease both by American Thyroid Association (ATA) and European Society for Medical Oncology (ESMO) recent guidelines.

Aim: The aim of our study was to assess the relationship between resection margin status (R0 vs R1) and the clinical outcomes (response to therapy, recurrence presence) in Polish patients with PTC.

Materials and Methods: A retrospective analysis of 2674 patients, who were enrolled to the study, from a single tertriary oncologic referential centre, operated between 2000-2021, was performed. From this group 1975 patients were further qulified for study: 1819 who had R0 resection status and were assessed as having low-risk cancer according to ATA guidelines (ATA-LR) and 156 who were treated as high-risk cancer (HR-ATA) only due to incomplete microscopic tumor resection (R1).

Results: In the group with R0 resection the excellent response to therapy, at the end of follow-up, was observed in 1738 (95.55%) patients and indeterminate response was observed in 76 (4.18%) cases. The biochemical incomplete response to therapy, during last follow-up, was detected in 1 (0.05%) patient. Structural incomplete response was stated in 4 cases (0.22%). There were 11 cases of reccurence (definied as diagnosing cancer after achieving so-called ’’no evidence of disease’’ due to prior treatment) of which 10 (90.91%) were treated succesfully and excellent response was achieved. In total, the risk of recurrence/persistent disease in patients with R0 resection was 5.24% (91/1738). In the group with R1 resection the excellent response to therapy was observed in 139 (89.1%) patients and indeterminate in 11 (7.05%) cases. The biochemical incomplete response to therapy was detected in 3 (1.92%) patient. Structural incomplete response was stated in 3 cases (1.92%). There were 2 cases of reccurence of which none achieved excellent response. In total, the risk of recurrence/persistent disease in patients with R1 resection was 10.9% (17/156).

Conlusions: Due to lower risk of unfavourable outcomes when incomplete microscopic resection is observed in differentiated thyroid cancer the consideration of treating cases with R1 feature as ’’intermediate cancer’’ for recurrence/persistent disease should be made.