Survival Improvement in Patients With Medullary Thyroid Carcinoma Who Undergo Pretargeted Anti–Carcinoembryonic-Antigen Radioimmunotherapy: A Collaborative Study With the French Endocrine Tumor Group

Abstract

No effective therapy is currently available for the management of patients with metastatic medullary thyroid carcinoma (MTC). The efficacy of pretargeted radioimmunotherapy (pRAIT) with bispecific monoclonal antibody (BsMAb) and a iodine-131 (131I) -labeled bivalent hapten is evaluated. Twenty-nine patients with advanced, progressive MTC, as documented by short serum calcitonin doubling times (Ct DTs), received an anti-carcinoembryonic antigen (CEA)/anti-diethylenetriamine pentaacetic acid (DTPA) -indium BsMAb, followed 4 days later by a 131I-labeled bivalent hapten. Overall survival (OS) was compared with 39 contemporaneous untreated MTC patients with comparable prognostic indicators. OS was significantly longer in high-risk, treated patients (Ct DT < 2 years) than in high-risk, untreated patients (median OS, 110 v 61 months; P < .030). Forty-seven percent of patients, defined as biologic responders by a more than 100% increase in CtDT, experienced significantly longer survival than nonresponders (median OS, 159 v 109 months; P < .035) and untreated patients (median OS, 159 v 61 months; P < .010). Treated patients with bone/bone-marrow disease had a longer survival than patients without such involvement (10-year OS, 83% v 14%; P < .023). Toxicity was mainly hematologic and related to bone/bone-marrow tumor spread. pRAIT against CEA induced long-term disease stabilization and a significantly longer survival in high-risk patients with Ct DTs less than 2 years, compared with similarly high-risk, untreated patients. Ct DT and bone-marrow involvement appear to be prognostic indicators in MTC patients who undergo pRAIT.