Young patients with acute lymphocytic leukemia, the most common type of pediatric cancer, are likely to report that they adhered to their anti-cancer medication better than they really did.

And so do their parents.

Studies show that over 95 percent of prescribed doses must be taken to be effective but a new analysis instead finds that that 84 percent of patients or their parents over-reported adherence to a regimen of the oral maintenance therapy6-mercaptopurine (6MP), which is prescribed for two years after chemotherapy for patients to achieve durable remissions.

Smita Bhatia, MD, MPH, of the University of Alabama at Birmingham, and colleagues gave 416 pediatric acute lymphocytic leukemia  patients from 87 participating institutions across the United States prescription pill bottles for their 6MP that contained a microprocessor chip in the cap to log the date and time the bottle was opened. These logs were then compared against self-report questionnaires completed by patients or their parents and provided to their physicians at monthly check-ups.

In addition to observing a majority of patients over-reporting the number of days that they had taken their medications, researchers observed a direct inverse trend in over-reporting. Of those found to adhere to their regimens (defined as taking their prescribed dose 95% of the time), a small percentage (8%) over-reported their intake. However, among those found non-adherent, a substantially larger percent (47%) over-reported. "We observed that there was an inverse relationship between over-reporting and the extent of non-adherence," said Dr. Bhatia.