Identification process for eligible studies.

<p>Identification process for eligible studies.</p

Comparison of overall survival between combined inhibition therapy and single inhibition therapy.

<p>Comparison of overall survival between combined inhibition therapy and single inhibition therapy.</p

Comparison of objective tumor response rate between combined inhibition therapy and single inhibition therapy.

<p>Comparison of objective tumor response rate between combined inhibition therapy and single inhibition therapy.</p

Comparison of progression-free survival between combined inhibition therapy and single inhibition therapy.

<p>Comparison of progression-free survival between combined inhibition therapy and single inhibition therapy.</p

Characteristics of included trials.

<p>Abbreviations: NR, not reported; PD, disease progression; PT, prohibitive toxicity.</p

Summary of toxicities grade 3 or greater.

<p>Summary of toxicities grade 3 or greater.</p