The placebo effect in thyroid cancer: a meta-analysis.

CONTEXT: The natural history of advanced thyroid malignancies is largely unknown. The outcome of patients included in the placebo arm of clinical trials could be reflective of their therapy-free evolution.

OBJECTIVE

To analyze the response rate, symptoms and adverse effects of locally advanced or metastatic differentiated (DTC) and medullary thyroid cancer (MTC) in patients treated with placebo in clinical trials.

DESIGN

PubMed (MEDLINE) and SCOPUS databases were searched through September 2015 to identify high-quality randomized controlled clinical trials. We included studies that recruited patients with DTC or MTC with a placebo arm.

METHODS

We conducted a meta-analysis for each category of response rate, adherence to treatment, and adverse events. An empirical Bayesian random-effect model was used.

RESULTS

We identified five clinical trials. DTC and MTC were independently analyzed. In the placebo arm, no complete response was observed; partial response occurred in 1.6% (0.6-3) and 6.4% (3.4-10.3) of DTC and MTC respectively; stable disease was described in 40.5% (34.6-46.9) and 53.9% (44.3-64.4) of DTC and MTC respectively. DTC reached a disease control rate of 42.3% (36.2-48.9) and MTC of 60.2 (50.1-71.4). Treatment discontinuation rate was 3.5% (1.9-5.5) in DTC and 5.7% (3.0-9.4) in MTC. Rate of dose reduction was 7.3% (4.8-10.5) in DTC and 6.2% (3.3-10.0) in MTC.

CONCLUSIONS

This meta-analysis provides extensive data on the response rate and adverse effects of locally advanced or metastatic DTC and MTC in patients treated with placebo. These results may be used for comparisons with results from clinical trials without a placebo arm.