Adherence assessment using medication weight in a phase IIb clinical trial of difluoromethylornithine for the chemoprevention of skin cancer.
OBJECTIVE
Adherence is a common and essential measurement in clinical trials. This study evaluates the association between participant self-reported study diary records and the weight of the medication vessel at each study visit, in the setting of a phase IIb topical chemoprevention trial.


METHODS
One hundred and twenty-four eligible participants were randomized to one of four arms [34 to difluoromethylornithine (DFMO) plus triamcinolone, 31 to DFMO plus placebo, 31 to placebo plus triamcinolone, and 28 to double placebo] for 6 months of treatment for actinic keratosis. Adherence was assessed at each clinic visit by weighing each tube of dispensed and returned medication and the participant's study diary.


RESULTS
Self-reported adherence was consistently higher than adherence measured by returned medication weight (96.5% versus 71.3%, 94.6% versus 82.4%, 95.3% versus 69.5%, and 95.8% versus 66.8% for DFMO, DFMO placebo, triamcinolone, and triamcinolone placebo, respectively; P < 0.001). Most participants (59.2%) recorded 100% adherence on the study diary; however, using the weight adherence, only 10.2% were completely adherent to the study regimen.


CONCLUSIONS
Self-reported diary measures seem to overestimate adherence when compared with weighing the returned medication vessel. It is recommended that future clinical trials involving topical applications incorporate medication weights as a primary measure of adherence because it is objective, quantitative, inexpensive, noninvasive, and easy to use.
Hess
Lisa M
LM
Arizona Cancer Center, University of Arizona, P.O. Box 245024, 1515 North Campbell Avenue, 2964A1 Tucson, AZ 85724, USA. hess@u.arizona.edu
Saboda
Kathylynn
K
Malone
Daniel C
DC
Salasche
Stuart
S
Warneke
James
J
Alberts
David S
DS
D000287:Administration, Topical; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000627:therapeutic use*; D018890:Chemoprevention; D000518:Eflornithine / Q000008:administration & dosage* / Q000627:therapeutic use*; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D010349:Patient Compliance; D010919:Placebos; D012878:Skin Neoplasms / Q000517:prevention & control*; D014221:Triamcinolone / Q000008:administration & dosage / Q000627:therapeutic use; D014342:Truth Disclosure
D000970:Antineoplastic Agents; D005938:Glucocorticoids; D010919:Placebos; D014221:Triamcinolone; D000518:Eflornithine