SEARCH STRATEGY
We used electronic search techniques of 27 computerized databases to conduct a comprehensive search. Keywords used were relevant terms from four categories: population, treatment, domain, and design. We identified grey literature through electronic searches of popular search engines, unpublished dissertations/theses, and cancer-related organizations and conferences. In addition, we searched reference lists from included individual studies for potential studies to consider. The dates of the last search for electronic databases and grey literature were November 2013 and October 2012, respectively.