PURPOSE: The need for international collaboration in cancer clinical trials has grown stronger as we have made progress both in cancer treatment and screening. We sought to identify those efforts already underway which facilitate such collaboration, as well as barriers to greater collaboration.

METHODS: We reviewed the collective experiences of many cooperative groups, governmental organizations, nongovernmental organizations, and academic investigators in their work to build international collaboration in cancer clinical trials across multiple disease sites.

RESULTS: More than a decade of work has led to effective global harmonization for many of the elements critical to cancer clinical trials. Many barriers remain, but effective international collaboration in academic cancer treatment trials should become the norm, rather than the exception.

CONCLUSION: Our ability to strengthen international collaborations will result in maximization of our resources and patients, permitting us to change practice by establishing more effective therapeutic strategies. Regulatory, logistical, and financial hurdles, however, often hamper the conduct of joint trials. We must work together as a global community to overcome these barriers so that we may continue to improve cancer treatment for patients around the world.