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Prospective cohort study: whether or not patients benefit from participation itself in randomized-controlled trials (SELECT BC ECO).

The randomized-controlled trial is widely accepted as a clinical trial to decide a standard therapy. It remains to be concluded whether or not patients benefit from participation itself in a randomized-controlled trial. This study was aimed at comparing prognoses between trial participants and participation-refusers. Concerned randomized trials are 'selection of effective chemotherapy for breast cancer' (SELECT BC) and its successor trial, SELECT BC-CONFIRM. Study subjects are all of metastatic breast cancer patients who are requested by their doctors to participate in these two trials. This trial is a hitherto exceptional prospective study and is suitable to clarify the effects of participation per se in such a trial on prognosis when compared with previous two studies.