Endocrine Abstracts

Introduction: The role of external beam radiotherapy (EBRT) as primary or as adjuvant therapy in the non-undifferentiated thyroid cancer (NUTC) is controversial. Most published data refer to retrospective case series. Therefore, little is known about the correlation between tumor markers and radiologic measurements of tumor response.

Objectives: The study aimed to analyze the kinetics of tumor markers and radiologic measurement of tumor response after EBRT in NUTC.

Material and methods: A retrospective analysis of a series of 11 patients diagnosed of NUTC, and consecutively treated with EBRT in the Clínica Universidad de Navarra (CUN) between 2010 and 2016 was performed.

Results: Clinical characteristics: gender: women (7) and men (4); age at diagnosis: 66 years (49–68); histological subtype: follicular (7), papillary (3), and medullary (1). EBRT techniques: intensity modulation radiotherapy (IMRT) (7), three-dimensional conformal radiotherapy (3D-RTC) (3) and radiosurgery (1). The median dose of EBRT was between 21 Gy and 76 Gy, and 18 Gy for radiosurgery. Localization of EBRT: bone (7), cervical (2), cervical-mediastinal (1) and cerebral (1) region. The most frequent adverse effects were dysphagia (three patients) and dermatitis (two patients). The toxicity grade according to the criteria of the Radiation Therapy Oncology Group (RTOG) was: 1–2 (4 patients) and 3 (1 patient). The twelve-month radiological response related to the area of EBRT administration, but not with other concomitant metastasis was: stability in 5 (3 follicular, 2 papillary), regression in 2 (both follicular), and progression in 4 patients (2 follicular, 1 papillary, and 1 medullary). In the 4 patients with follicular cancer showing stability or regression, a parallel reduction in thyroglobulin levels was observed at 6 and 12 months. In the patient with medullary cancer, we observed correlation between the radiological progression and calcitonin increase at 5 years.

Conclusions: In our series, we observed a correlation between the response to EBRT regarding the tumor burden and the corresponding thyroid marker: decreasing thyroglobulin levels in follicular thyroid cancers showing stability and regression, and increasing calcitonin levels in the medullary cancer showing progression.