title: Latency Period until the Development of Thyroid Cancer in Young Patients Submitted to Radiotherapy: Report of 10 Cases.
abstract: BACKGROUND
  Radiotherapy increases the risk of thyroid cancer (TC); patients submitted to this treatment should undergo a long-term follow-up. Our aim is to describe the features and outcomes of young patients who developed TC after radiotherapy.
  
  
  METHODS
  At our center, patients undergoing radiotherapy directly or indirectly involving the thyroid are regularly followed up in order to detect early dysfunction or nodules. Herein, we report the cases of 10 patients who were submitted to radiotherapy and developed TC.
  
  
  RESULTS
  Seven patients were irradiated in the neck and 3 in nearby regions. The mean age at the last radiotherapy session was 10 ± 5.5 years. The average time until the appearance of the first thyroid nodule was 14 ± 4.7 years. The mean size increment of the nodules was 2.4 ± 1.6 mm/year. On the first cytology, only 2 results were suspicious of papillary thyroid cancer (PTC). All patients presented a histology of PTC. Eight were in stage I and 2 in stage II. The median follow-up from primary diagnosis to TC and beyond was 20 and 3 years, respectively.
  
  
  CONCLUSIONS
  In these patients, cytologies may be difficult to interpret due to persistent benign results. The threshold for surgical indication may be anticipated, considering the increased risk of TC. We report the evolution of these nodules over time, from the end of primary oncological treatment.
authors.affiliation: Endocrinology Department, Instituto Português de Oncologia de Lisboa, Francisco Gentil, Lisbon, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Simões-Pereira
authors.affiliation: Endocrinology Department, Instituto Português de Oncologia de Lisboa, Francisco Gentil, Lisbon, Portugal.
authors.forename: Margarida Silva
authors.initials: MS
authors.lastname: Vieira
authors.affiliation: Endocrinology Department, Instituto Português de Oncologia de Lisboa, Francisco Gentil, Lisbon, Portugal.
authors.forename: Maria Conceição
authors.initials: MC
authors.lastname: Pereira
keywords: Cancer survivors; Radiation-related cancer; Radiotherapy; Thyroid cancer