Prospective evaluation of two recruitment strategies for a randomized controlled cancer prevention trial

To evaluate two recruitment strategies used during the full-scale randomized, placebo-controlled Selenium and Vitamin E Cancer Prevention Trial (SELECT) at one clinical center.

Recruitment of participants to cancer prevention trials is challenging and costly and more efficient methods are needed.

SELECT participants were males ≥60 years old who were solicited with two recruitment strategies. In the control strategy, potential participants, identified through purchased mailing lists, were sent a SELECT invitation letter. In the 'spouse' strategy, letters were sent to married postmenopausal women already participating in the Women's Health Initiative (WHI) at our clinical center asking them to provide an enclosed SELECT invitation letter (identical to the one in the control strategy) to the 'man in her life'. Our hypothesis was that SELECT recruitment of men would be enhanced by this indirect mailing to their spouses already participating in a similar program.

In the control strategy, 183,315 invitation letters were mailed to 60,000 men; cumulative response was 2.16%; 600 men ultimately enrolled in SELECT (15.1% of respondents) for a mailing recruitment cost of $259 per participant. In the spouse strategy, 800 women participating in WHI clinical studies had husbands; of the 2214 invitation letters mailed to this group of women, cumulative response was 2.75%; 34 men ultimately enrolled in SELECT (55.7% of respondents) for a mailing recruitment cost of $59 per participant.

Process information on how invitation letters were handled in the spouse strategy was not collected.

A direct mail recruitment strategy was successful in recruiting men to a cancer prevention trial. A recruitment strategy involving indirect mailing to married women participating in a similar research program in the same center did not increase initial response substantially, but a higher proportion of respondents ultimately entered the prevention trial.