Abstract LB-219: Elevated expression of cellular proliferative index MIB-1 in post-Chornobyl papillary thyroid carcinoma with coexisting thyroiditis

Abstract

Abstract Introduction: Most patients with papillary thyroid cancer (PTC) have an excellent prognosis. Ki-67 is marker of proliferation, and proliferative index more than 5% as calculated with the MIB-1 antibody indicates a worse prognosis in PTC. This study was performed in order to investigate and evaluate expression of MIB-1 in a cohort of adult PTC patients who were exposed in their childhood to radioactivity from the Chornobyl accident in 1986. Materials and Methods: 70 patients (60 females and 10 males, mean age 30,5 (19-39)) operated on for PTC during 2004-2008 were identified for the study. Two groups were established according to diagnosis. Group 1 consisted of patients with PTC only (n=53). Group 2 consisted of patients with PTC and co-existing chronic lymphatic thyroiditis (n= 17). Proliferative activity was measured by immunohistochemistry using monoclonal MIB-1 antibody against nuclear factor Ki-67. A minimum of 2000 tumor cells were calculated and the percentage of positive cells (MIB-1 index) was compared with clinical data. Results: MIB-1 index was higher in Group 2 (mean 3,65) compared with Group 1 (mean 1,97) (p=0,005). No other clinical features could be correlated with the MIB-1 index. 26% of patients in Group 1 had lymph node metastases, and 23% in Group 2. The mean tumor size was slightly higher in Group 1 (2 cm) compared with Group 2 (1,75 cm). Age at diagnosis (30,5) and age at the Chornobyl accident (11) were identical between the groups. Conclusions: The clinical features of this cohort of adult PTC patients exposed to the radioactive fallout from the Chornobyl accident seem no different to other PTC cohorts. However, a rather large proportion of patients showed signs of coexisting thyroiditis. Whether the elevated MIB-1 index in this group of patients reflects a worse prognosis is yet not possible to say due to the short follow-up time. Still, a closer follow-up may be justified. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-219.