Downstaging of Thyroid Cancer Does Not Necessarily Imply Lower Mortality

  • Background According to the new 8th AJCC/TNM edition, we investigated the effect of downstaging in patients with thyroid cancer (TC).

    Methods From a large cohort of patients actively followed-up for TC since 2002, we retrospectively reviewed 46 with disease-specific mortality (17 males, 29 females and mean age 67±13,96yrs). 

    Results Histologically, TCs were: papillary (PTC) in 16 cases (35%), follicular in 8 (17%), both PTC and Hurthle cancer in 1 (2%), poorly differentiated (PD) in 6 (13%), anaplastic in 5 (11%) and medullary in 6 (13%). No histological diagnosis was available in 4. On diagnosis, 10 patients were aged <55yrs. In patients with PD TC and well-differentiated (WD) TC, disease-specific deaths occurred in 19. TNM stages were downgraded in 11 of these (58%): 6 patients from stage III to II; 3 patients from stage IV to III; and 2 patients from stage IV to II. Their mean age was 64yrs; 4 were aged <55yrs. Ten patients underwent radioactive iodine ablation (RAI) with a mean dose of 370mCi. Post-thyroidectomy baseline thyroglobulin levels in this subgroup of patients were >10 µg/L in 6, >2 µg/L in 1, 0-2 µg/L in 2 and unknown in 1. Patients downgraded from stage IV/III to stage II had lymph node metastases (38%) or distant metastases (60%), received treatment with Tyrosine-Kinase Inhibitors (50%) and underwent more than 1 course of RAI (50%) during their disease.  

    Conclusion In PD TC and WD TC patients downgraded from stage IV/III to stage II, the severity of disease should not be underestimated. A more accurate assessment of their mortality risk can be obtained by integrating TNM stage and post-thyroidectomy thyroglobulin levels.

 

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