Bone metastases of differentiated thyroid cancer: impact of early 131I-based detection on outcome

Abstract

Bone is the second most frequent target of distant metastases in patients with differentiated thyroid cancer, and such forms carry a very poor prognosis. The impact of 131 I therapy in this setting is controversial. We describe the diagnostic circumstances and outcome of patients with bone metastases recently managed in two institutions. Among 921 consecutive thyroid cancer patients who had total thyroidectomy and 131 I ablation between January 2000 and December 2004 and who were subsequently monitored, bone metastases had been diagnosed in 16 patients. In three cases, the bone metastases were non-functioning (negative 131 I uptake) . These patients were treated with surgery and radiotherapy but progressed rapidly. The other 13 patients had functioning (positive 131 I uptake) bone metastases. In five of them, thyroid cancer was revealed by signs of distant involvement (bone pain, nZ4; dyspnea, nZ1). The bone metastases progressed in these five patients, despite local therapy and multiple courses of 131 I. The bone metastases in the remaining eight patients were discovered on the postsurgery 131 I therapy scan. Complementary radiological studies were negative except in one patient in whom one of the metastases (a 5 mm lesion of the right humerus) was visible on magnetic resonance imaging (MRI). Six of these patients showed a good response to 131 I therapy, with 131 I uptake and Tg levels becoming undetectable or showing a sharp fall. One patient refused 131 I therapy; bone metastases became visible on MRI within 1 year and the Tg level rose tenfold. The disease progressed in one patient despite 131 I therapy. Post-surgical 131 I ablation can contribute to early detection of bone metastases at a time when the Tg level may be only moderately elevated, when other radiological studies are negative, and when the disease is potentially curable by 131 I therapy.

A low thyroglobulin level cannot be used to avoid adjuvant 131I therapy after thyroidectomy for thyroid carcinoma

“…However, one important message of the study by Park et al [1] is that Tg levels cannot be used to decide whether postsurgical ablation should be performed or not. This is in agreement with other data showing that the number of patients with lung or bone metastases can be discovered during 131 I ablation even in the presence of low or nonsuspicious Tg levels and negative radiological studies [10][11][12]. At this stage, a complete remission can be obtained using a limited number of 131 I courses; hence the importance in clinical practice of not relying on Tg alone.…”

Radioiodine treatment after surgery for differentiated thyroid cancer: a reasonable option

“…Notably, in about 5% of patients, the 131 I whole-body scan has uncovered occult distant spread, mainly pulmonary or skeletal metastases [18,[36][37][38][39]. This small percentage of cases has its importance as distant metastases are the main purveyors of death from DTC and early detection on the 131 I scan is a favorable situation that offers chances for cure [18,[36][37][38][39].…”

Early prognostic factors at the time of diagnosis of bone metastasis in patients with bone metastases of differentiated thyroid carcinoma

“…Metachronous metastasis is defined as distant metastasis found during the follow-up. However, patients who have no symptoms or SRE and just detected bone metastasis by initial RAIT demonstrate excellent responses to RAIT and much better survival than patients who demonstrate bone metastasis before the initial RAIT (5,13). Furthermore, patients who demonstrate bone metastasis through an initial RAIT often include bone metastasis with no structural correlation, which is known to have no prognostic significance (14).…”