[Surveillance after treatment of differentiated thyroid cancers]

The prognosis of differentiated thyroid carcinoma mainly depends on the quality of the initial treatment and on early detection and management of any recurrences.

The aim of this retrospective study was to assess the modalities and duration of surveillance in these patients according to an original classification based on the initial extent of the tumour.

The modalities of detection of local recurrences and metastases and the date of the latest recurrences were assessed in a series of 509 patients with a mean follow-up of 8.2 years (range: 1 to 25 years). Most patients were treated by total thyroidectomy, followed by a therapeutic dose of radioactive iodine. The other patients with a small localized carcinoma underwent partial thyroidectomy without radioactive iodine. Patients were divided into four groups on the 7th postoperative month after follow-up scintigraphy and thyroglobulin assay: group I: microcancers (n = 117), group II: cancer without lymph node involvement or metastasis and normal thyroglobulin divided into IIA, age < 45 years (n = 100) and IIB, age > 45 (n = 94), group III: cancer with lymph node involvement and normal thyroglobulin (n = 102), group IV: high-risk cancers with metastases or regional extension other than lymph node extension or thyroglobulin > 3 micrograms/L (n = 96).

Cancer-dependent actuarial survival rates for groups I, IIA, IIB, III, IV were 100%, 100%, 96%, 100%, and 73% at 10 years and 100%, 100%, 92%, 100%, and 86% at 15 years, respectively. Local or metastatic recurrences were sometimes detected by a single follow-up examination, while the other examinations were negative: cervical palpation, thyroglobulin assay, iodine scintigraphy, chest X-rays. The latest recurrences were observed at 12 years in groups I and IIA and at 16 years in groups IIB, III, and IV with normal thyroglobulin.

This study confirms the importance of weaning thyroglobulin assays and scintigraphy which must be repeated every 5 years. Cervical palpation, thyroglobulin assay without weaning, chest X-rays may also detect recurrences. Duration of follow-up must be adapted to the initial extension and subsequent course: 15 years in groups I and IIA, 20 years in groups IIB, III, and IV with normal thyroglobulin, for at least 10 years after each recurrence, and life-long in the case of progression and thyroglobulin > 3 micrograms/L. Patients must be informed about the duration of follow-up at the 7th month when the definitive classification can be established and continuity of this follow-up must be documented in a special register.