ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2019) 63 P746 | DOI: 10.1530/endoabs.63.P746

External beam radiotherapy in differentiated thyroid cancer: clinical experience in a large spainish multicentre study

Ana Romero-Lluch1, Emma Anda2, Javier Santamaría3, Juan José Díez4, Sergio Donnay5, Juan Carlos Galofré6, Edelmiro Menéndez7, Begoña Pérez8, Julia Sastre9, Victoria Alcázar10, Concepción Blanco11, Pedro Iglesias12, Ma José Pamplona13 & Elena Navarro1

1Department of Endocrinology, Hospital Universitario Virgen del Rocío, Sevilla, Spain; 2Department of Endocrinology, Complejo Hospitalario de Navarra, Pamplona, Spain; 3Department of Endocrinology, Hospital Universitario Cruces, Vizcaya, Spain; 4Department of Endocrinology, Hospital Universitario Ramón y Cajal, Madrid, Spain; 5Hospital Universitario Fundación Alcorcón, Madrid, Spain; 6Department of Endocrinology, Clínica Universidad de Navarra, Pamplona, Spain; 7Department of Endocrinology, Hospital Universitario Central de Asturias, Oviedo, Spain; 8Department of Endocrinology, Complejo Asistencial Universitario de León, León, Spain; 9Department of Endocrinology, Complejo Hospitalario de Toledo, Toledo, Spain; 10Department of Endocrinology, Hospital Severo Ochoa, Madrid, Spain; 11Department of Endocrinology, Hospital Príncipe de Asturias, Madrid, Spain; 12Departments of Endocrinology, Hospital Universitario Ramón y Cajal and Hospital Universitario Puerta de Hierro-Majadahonda, Madrid, Spain; 13Department of Endocrinology, Hospital Royo Villanova, Zaragoza, Spain.

The role of adjuvant external beam radiotherapy (EBRT) in differenciated thyroid cancer (DTC) is controversial. It remains unknown whether EBRT in the neck following conventional treatment might improve progression-free survival (PFS) and overall survival (OS).

Objective: To assess EBRT outcomes in patients with locally advanced DTC in terms of local disease progression, PFS and OS.

Material and Methods: A multicentric retrospective study was performed including all those patients diagnosed of DTC and treated with EBRT in the neck or mediastinum as a consequence of incomplete resection, extrathyroidal extension (ETE) and/or local recurrence after surgery. Quantitative variables expressed as median [interquartile range].

Results: Sixty-seven patients (48 women; age at diagnosis 62 [51–70] years) from 11 different hospitals in Spain were included. 32.3% (n=23) of cases had an aggressive histologic variant. 75.8% (n=50) of tumours had the resection margins involved, 86.4% (n=57) had ETE and extranodal extension was present in 43.8% (n=28). Iodine-refractory patients were 73.8% (n=48). Age at EBRT time was 68 [59–77] years. Radiotherapy was administered mainly in the neck (74.6%), followed by neck and mediastinum (22.4%). Conventional EBRT was used in 38.6% of patients, followed by IMRT (35.1%) and 3DRT (19.3%). The median dose was 60 [50–66] Gy. Indications of EBRT were ETE in 50.7%, disease persistence/recurrence after surgery (34.3%), extranodal extension and high-risk histology (7.5% each one). The median follow-up period after EBRT was 41 [18–69] months. Thyroglobulin decreased or stabilized in 84.6% of patients without distant metastases during the follow-up. In this group (M0, n=39) radiotherapy stabilized or reduced structural local disease in 96.8%, 96% and 92.9% at 1, 2 and 5 years, respectively. In M1 patients (n=25), EBRT stabilized or reduced cervical/mediastinal disease in 64.3%, 56.2%, 50% at 1, 2 and 5 years. OS rate was 68.7% (mean OS 10.9 years; CI 95%, 8.8–12.9). EBRT dose ≥60 Gy was associated with an increase in mean OS compared with dose <60Gy (11.2 vs 6.9 years, P=0.01). Patients <55 years had longer mean OS than those ≥55 years (15.7 vs 7.2 years, P=0.004). The location of EBRT (neck or mediastinum) was associated with different means of OS. Type of histology or positive surgical margins were also related with different mean PFS.

Conclusions: In our experience, adjuvant EBRT was useful to control local disease in aggressive DTC. Location of therapy (neck), age <55 and EBRT dose ≥60 Gy could be predictors of better clinical response to treatment.