A phase II trial of ZD6474 in patients with hereditary metastatic medullary thyroid cancer

Abstract

5533 Background: Medullary thyroid carcinoma (MTC) is the most common cause of death in patients with hereditary syndromes caused by specific mutations in the RET protooncogene. RET activation is the oncogenic event, which results in intrinsic RET receptor tyrosine kinase activity, but other pathways, such as VEGFR- and EGFR-dependent signaling, also participate in tumor growth and development. ZD6474 is a once-daily oral agent that selectively targets RET, VEGFR and EGFR tyrosine kinases. The clinical activity of ZD6474 was evaluated in patients with hereditary MTC. Methods: In this open-label Phase II study, patients with unresectable, measurable, locally advanced or metastatic hereditary MTC and a RET germline mutation received once-daily oral doses of ZD6474 300 mg. The primary objective was to assess the objective tumor response (RECIST). Secondary objectives included assessments of biochemical response (determined by changes in plasma levels of calcitonin [CTN]) and safety/tolerability of ZD6474. An exploratory objective was to measure plasma levels of carcinoembryonic antigen (CEA). Results: As of 30 November 2005, 16 patients (6 male/10 female; median age 50 years, range 22–77) had entered the study and received initial treatment with ZD6474 300mg. The median duration of treatment was 136 days (range 16–353). Fifteen patients were evaluable for tumor response, CTN, and CEA. Objective tumor assessments have demonstrated partial responses in 3 patients (n = 2 confirmed; n = 1 unconfirmed), stable disease in 10 patients (n = 8, ≥8 and <24 weeks; n = 2, ≥24 weeks) and progressive disease in 2 patients. A >50% decrease from baseline in plasma CTN levels has been maintained for at least 4 weeks in 12/15 patients; a decrease in plasma CEA levels of the same magnitude and duration has been observed in 6/15 patients. Common adverse events (AEs) were diarrhea (n = 12) and nausea, rash and fatigue (each n = 11). CTC grade 3 AEs attributable to ZD6474 were QTc interval prolongation (n = 3), and diarrhea, skin rash and hypertension (each n = 2). Conclusions: ZD6474 shows promising evidence of clinical activity in patients with hereditary MTC. These are preliminary data and patients are still being recruited to this ongoing study. [Table: see text]