6-Mercaptopurine (6MP) is an oral chemotherapy drug often used to treat acute lymphocytic leukaemia (ALL), the most common blood cancer in children.

While taking 6MP daily during maintenance therapy as prescribed by a doctor is critical to sustaining durable remissions, not all children take their medicine as directed.

Asking patients to self-report their intake of 6MP is convenient, inexpensive, and helps doctors understand if doses are being missed and interventions are needed.

However, previous studies not related to oncology show that patients often report that they took their medicine even if they missed doses.

This study aimed to compare self-reported 6MP intake with electronic monitoring to identify predictors of over-reporting of 6MP intake.

Participants included 416 children with ALL in their first remission who were prescribed oral 6MP.

The patients’ ages ranged from 2 to 20 years old.

Treatment intake for each patient was measured electronically using a system that recorded each date and time the 6MP bottle was opened during a span of four months.

At the end of each of the four months, the child or parent reported the number of days that 6MP had been taken during the preceding month.

Patients were then categorised as perfect reporters if the self-report matched the electronic report, over-reporters if the self-report indicated more doses than the electronic report by five or more days per month for more than half of months of monitoring, or “others.”

Only 12 percent of patients were identified as perfect reporters; 23.6 percent were over-reporters, and 64.4 percent were considered “others.”

Upon further analysis, researchers found that for each increasing year of age of the child, the risk of over-reporting increased by seven percent.

Race was also a factor, as Hispanic children/parents were 2.4 times more likely to over-report, Asians were 3.1 times more likely to over-report, and African Americans were 5.3 times more likely to over-report when compared with non-Hispanic white children/parents.

Children whose father did not attend college were 2.1 times more likely to over-report.

Finally, children who did not adhere to their 6MP regimen (i.e., those whose adherence rate was less than 95% of prescribed doses) were 8.6 times more likely to overstate their monthly doses, when compared with children who adhered to prescribed 6MP.

While 78.6 percent of over-reporters were non-adherent, only one of 50 (2%) of the perfect reporters were non-adherent.

Researchers conclude that approximately 25 percent of children/parents over-report 6MP intake; and over-reporting is more likely in patients who are non-adherent to 6MP, older, of a minority race, and from households with lower paternal education.

These findings suggest that subjective reporting of 6MP ingestion during maintenance therapy for childhood ALL should be used with caution.

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Source: ASH