Phase II trial of anticarcinoembryonic antigen pretargeted radioimmunotherapy in progressive metastatic medullary thyroid carcinoma: biomarker response and survival improvement.

UNLABELLED: The prognosis of medullary thyroid carcinoma (MTC) varies from long- to short-term survival based on such prognostic factors as serum calcitonin and carcinoembryonic antigen (CEA) doubling times (DTs). This prospective phase II multicenter trial evaluated the efficacy and safety of anti-CEA pretargeted radioimmunotherapy (pRAIT) in rapidly progressing metastatic MTC patients and also how serum biomarker DTs correlate with clinical outcome.

METHODS

From June 2004 to January 2008, 42 patients were treated with anti-CEA × anti-diethylenetriaminepentaacetic acid (DTPA) bispecific antibody (hMN-14 × m734) (40 mg/m(2)), followed by (131)I-di-DTPA-indium bivalent hapten (1.8 GBq/m(2)) 4-6 d later.

RESULTS

The disease control rate (durable stabilization plus objective response) was 76.2%. Grade 3-4 hematologic toxicity was observed in 54.7% of patients and myelodysplastic syndrome in 2, including 1 heavily treated previously. After pRAIT, 21 of 37 assessed patients (56.7%) showed a significant impact on DT (≥100% increase of pre-pRAIT calcitonin or CEA DT or prolonged decrease of the biomarker concentration after pRAIT). Pre-pRAIT DT and post-pRAIT DT were significant independent predictors for overall survival (OS) from pRAIT (pre-pRAIT: hazard ratio [HR], 0.46; 95% confidence interval [CI], 0.24-0.86; P = 0.016; and post-pRAIT: HR, 5.32; 95% CI, 1.63-17.36; P = 0.006) and OS from diagnosis (pre-pRAIT: HR, 0.21; 95% CI, 0.08-0.51; P = 0.001; and post-pRAIT: HR, 6.16; 95% CI, 1.81-20.98; P = 0.004).

CONCLUSION

pRAIT showed antitumor activity, with manageable hematologic toxicity in progressive MTC. Increased biomarker DT after treatment correlated with increased OS.