Endocrine Abstracts

Introduction: Reliable prognostic factors are crucial to choose the optimal treatment strategy and follow-up for differentiated thyroid carcinomas (DTC) patients. Thus, the aim of the study was a retrospective evaluation of prognostic factors of cancer relapse in patients treated in a single institution.

Material: The study group consisted of 510 DTC patients, staged pT1b-T4N0-N1M0, treated with total thyroidectomy followed by complementary ¹³¹I therapy. In 71% papillary thyroid carcinoma was diagnosed, whereas in 29% – follicular thyroid cancer. Based on TNM classification (revised 1997), 11.6% patients were classified as T₁, 35.1% – T₂, 8.4% – T₃, 9,4% – T₄, and 35.5% as Tx. Lymph node metastases (N1) were present in 24.7% cases. Median follow-up was 12.1 years (range 1.5–15.2).

Results: Age at diagnosis, sex, thyroid capsule infiltration, multifocal tumor growth, tumor size, N1, stimulated serum thyroglobulin (Tg) level, and ¹³¹I thyroid remnant uptake evaluated before adjuvant ¹³¹I treatment were statistically significant in univariate analysis. Stimulated serum Tg >30 ng/ml was the most important, independent risk factor in a multivariate Cox regression analysis, and increasing the risk of cancer recurrence nearly sixfold. N1 was associated with a nearly fourfold increase in the risk of relapse. Other independent poor prognostic factors in a multivariate analysis were tumor size, age at diagnosis, and thyroid remnant uptake before ¹³¹I treatment. The risk of relapse in the study group was 12.55%. 5- and 10-year recurrence free survival were 90.1 and 87.5% respectively.

Conclusions: Serum stimulated Tg >30 ng/ml, measured after the surgery before radioiodine treatment, was the most significant independent prognostic factor. Age above 60 years, initial stage of the disease (tumor diameter and lymph node involvement) and low (<1%) postoperative thyroid ¹³¹I remnant uptake (T₂₄) independently increased the risk of relapse, whereas histopathological type and markers of tumor aggressiveness, such as thyroid capsule infiltration, multifocality, and angioinvasion did not influence recurrence free survival.