Thyroid Cancer Incidence in an HMO of Buenos Aires: Increase of the Incidence Rate of Incidental Thyroid Cancer

Program: Abstracts - Orals, Poster Previews, and Posters
Session: SAT 270-310-Thyroid Neoplasia (posters)
Saturday, April 2, 2016: 1:15 PM-3:15 PM
Exhibit/Poster Hall (BCEC)

Poster Board SAT 295
Maria Fabiana Russo Picasso*1, Jimena Vicens2, Carina Giuliani3, Carina Giuliani3, Ana Jaen3, Carmen Cabezon3, Silvana Figar3, Marcelo Figari3 and Patricia Fainstein Day4
1Hospital Italiano de Buenos Aires, Capital Federal, Argentina, 2Hospital Italiano de Buenso Aires, CABA, Argentina, 3Hospital Italiano de Buenos Aires, CABA, Argentina, 4Hospital Italiano de Buenos Aires, Buenos Aires, Argentina
Introduction:   Two hypothesis have been postulated to explain the increase of thyroid cancer (TC) incidence worldwide: an  excess of detection of subclinical,and ultimately clinically irrelevant disease, or a true increase of disease brought about by still unidentified environmental factors. Incidence rates of incidental TC may  clarify the  true significance of the increase of incidence  of TC.

Aim:  Our aim was to compare the epidemiological characteristics  of CT and incidence rates according to mechanism of detection  in a university  hospital-based HMO of Buenos Aires in two different periods.

Materials and Methods: Design: Observational, retrospective cohort. Methods: Our HMO comprises a significant sample of the population of Buenos Aires and its suburbs. All its members undergo surgery only in the same Medical Center, where  all medical records are electronically  managed since 2003. We identified incident cases of TC in our HMO  through de Pathology Division records.  Complete medical records of cases were then reviewed by the authors to valídate them as true incident TC, and to identify mechanisms of detection, clinical and pathologic characteristics. The Affiliation Registry was accessed to valídate affiliation and to calculate the population at risk at the time of diagnosis.  Patients with less tan 12 months´ affiliation prior to diagnosis were excluded of análisis.  TC incidence and characteristics were  grouped  in two periods 2003-2007 and  2008-2013 for comparison. . Incidence rates and incidence rate relative risk (IRR) according to mechanism of detection  were estimated for each period , and age-adjusted to the world population.      95% confidence intervals were calculated for each rate.  Quantitative variables were expressed as X+SDM or Median (IQR); qualitative variables were expressed in numbers (%). Incidence rates are expressed as 100000 person/year. Two tailed t- tests, X2 tests or  95% Confidence Intervals were used to compare both periods as appropiate. A p<0.05 was considered significant.

Results: 224 patients belonging to the HMO underwent surgery  for TC  between January 1st , 2003 and December 31st , 2013. The mean age at diagnosis 57 + 14 years; 81% were female, with a F/M ratio of 4.33; 88% were papillary thyroid carcinomas. The crude cumulative incidence rate for the period of 2008-2013 was 22.6 [19.47-26.15], which adjusted to world population (WHO 2001) was 16.01 (13.36-18.65). Incident TC was significantly smaller (10 [6-17] vs 14 [9-20] mm] (p<0.03) and incidental TC IRR was significantly higher [0.42 [0.301-0.57] vs 0.12 [0.04-0.30]] during 2008-2013 when compared to 2003-2007. 

Conclusions: There has been an increase of the incidence rate of incidental TC, mainly of smaller sized- TC,i n the population belonging to this HMO of Buenos Aires, which suggests  an excess of detection of subclinical disease. More studies are needed to confirm these results in other settings

Nothing to Disclose: MFR, JV, CG, CG, AJ, CC, SF, MF, PF

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