Initial results from a phase II trial of motesanib diphosphate (AMG 706) in patients with differentiated thyroid cancer (DTC)

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Background: This phase 2 study evaluated the safety and efficacy of AMG 706, an oral, investigational multikinase (MKI) inhibitor with antiangiogenic and direct antitumor activity achieved by selectively targeting VEGF, PDGF, and Kit receptors and RET, in pts with advanced DTC or medullary thyroid cancer (MTC). Presented here are results from the DTC stratum. Methods: This was a multicenter, phase 2, open-label, single-arm study of pts with advanced thyroid cancer stratified by DTC or MTC (planned n=80 each). The primary endpoint was objective tumor response per modified RECIST by independent central review. Secondary DTC endpoints were duration of response and progression-free survival (PFS). Pts = 18 yrs with progressive, 131I-resistant disease, ECOG 0–2, and no prior treatment with VEGFr MKIs received AMG 706 125mg QD until disease progression or unacceptable toxicity. Assessments included tumor response (q8w), pharmacokinetics (PK), and safety. Results: 93 pts with DTC were enrolled and received at least 1 dose of AMG 706. DTC subtypes were: papillary, 58%; Hürthle cell, 18%; follicular, 16%; other, 8%. Median (range) age was 62 (36–81) yrs. 20% of pts had prior chemotherapy; 96% had prior 131I therapy. With median follow-up of 32 wks, objective tumor response (CR or PR) rate (95% CI) was 12% (6.1, 20.2); SD, n=64 (69%; durable SD =24 wks, 24%); PD, n=7 (8%). Median (95% CI) time to response was 103 (53, 161) days; median PFS was 276 (221, not estimable) days. 85% of pts were alive >8 months after starting therapy. All pts (100%) had some treatment- emergent adverse events (AE): grade 3, 55%; grade 4, 10%; grade 5, 5% (all grade 5 were deemed unrelated to AMG 706). Common AEs included diarrhea (70%; 11% grade 3), fatigue (58%; 5% grade 3), hypertension (49%; 22% grade 3), headache (43%; 4% grade 3), nausea (40%; 2% grade 3), and hypothyroidism and/or increased TSH (17%; no grade 3); none of these were grade 4 or 5. 6% of pts had cholecystitis. PK results showed that AMG 706 PK at 125mg QD was comparable to data obtained in other monotherapy studies at the same dose level. Conclusions: In this study of pts with advanced 131I-resistant DTC, AMG 706 showed encouraging antitumor activity and had tolerable and manageable toxicities. Further investigation is warranted.

No significant financial relationships to disclose.

Papillary and follicular thyroid carcinoma

Papillary and follicular thyroid carcinomas are among the most curable of all cancers. However, some patients are at high risk of recurrence or even death from their cancer. Most of these patients can be identified at the time of diagnosis using well-established prognostic indicators. The extent of initial treatment and follow-up should therefore be individualized. The early discovery of persistent and recurrent disease is based on the combined use of serum thyroglobulin determination and of total body scanning with 131I. The recent availability of recombinant human thyroid stimulating hormone has greatly improved the quality of the patient's life during follow-up. Treatment of recurrences is based mainly on surgery and 131I treatment.

The role of recombinant thyroid-stimulating hormone (rhTSH) in the detection and management of well-differentiated thyroid carcinoma: a roundtable discussion

A Roundtable meeting of European endocrinologists and nuclear medicine physicians recently examined the role of recombinant human thyroid-stimulating hormone (rhTSH, Thyrogen, thyrotropin alfa, Genzyme Corporation, Cambridge, MA, USA) in the detection and management of well-differentiated thyroid carcinoma. The meeting sought to review clinical work to date and to provide guidance and perspective on the agent's application in everyday practice. The Roundtable included a panel discussion centering on three major topics: 1) rationale for use of exogenous versus endogenous TSH stimulation of radioiodine uptake and thyroglobulin (Tg) production; 2) impact and use of rhTSH in diagnostic follow-up; and 3) role of rhTSH in radioablation. The panel concluded that obtaining TSH stimulation of radioiodine uptake and Tg production exogenously with rhTSH obviates the weeks-long withdrawal from thyroid hormone suppression therapy (THST) needed to obtain such stimulation endogenously. rhTSH administration thereby eliminates morbidity, discomfort and uncertainties of compliance and timing associated with THST withdrawal. Thus compared to withdrawal, rhTSH administration offers important advantages in safety, quality of life, reliability, predictability and convenience to patients and care providers. rhTSH therefore represents a major advance in the diagnostic follow-up of well-differentiated thyroid cancer. By increasing the sensitivity of serum Tg testing during THST, rhTSH administration also improves the sensitivity of diagnostic follow-up. In addition, heightening the sensitivity of Tg testing may permit more selective application of iodine-131 whole body scanning, decreasing the invasiveness of diagnostic follow-up. Clinical studies are underway to confirm the preliminary promise of rhTSH as an adjunct to radioablation of normal or neoplastic thyroid tissue, with emphasis on the therapeutic setting.

Diagnostic follow-up of well-differentiated thyroid carcinoma: historical perspective and current status

Well-differentiated (follicular and papillary) thyroid carcinoma accounts for 80% to 90% of the approximately 28,000 new cases each year and the estimated 376,000 existing cases of primary thyroid cancer in Europe and the United States. It is among the most curable neoplasms, but 5% to 20% of survivors develop local or regional recurrences, and <5% to 10% distant metastases, generally in the first years of follow-up, but sometimes after many years. Outcome of patients with recurrent or metastatic disease is highly dependent on the size and extent of neoplastic foci when detected. Because of the long-term risk of recurrence and the importance of timely detection, diagnostic follow-up of well-differentiated thyroid carcinoma is life-long and must be very sensitive. The past three decades have seen great progress in improving the safety, efficacy and convenience of the diagnostic follow-up of well-differentiated thyroid cancer. Three major innovations account for this progress: 1) increased understanding of prognostic factors for disease recurrence and individualization of follow-up according to these factors; 2) the emergence of serum thyroglobulin (Tg) measurement as the principal modality in diagnostic follow-up; 3) and most recently, the introduction of recombinant human thyroid-stimulating hormone (rhTSH) to provide TSH stimulation during thyroid hormone suppression therapy (THST) and to avoid THST withdrawal for Tg testing or iodine-131 (I-131) whole-body scanning. Continued work in these three areas and in new areas will allow the thyroidology community to build on, and patients to benefit from recent progress.