Mercaptopurine (MP) Dose Intensity and Genetic Ancestry. For patients enrolled onto AALL03N1 protocol, MP dose was adjusted during maintenance therapy on the basis of host toxicities (myelosuppression and infections), and dose intensity was defined as ratio of prescribed dose over protocol planned dose (75 mg/m2 per day). Dose intensity was measured longitudinally over six months and is shown as a single cumulative value for the study period. Patients were grouped into five racial/ethnic categories on the basis of genetic ancestry. Genetically defined East Asians had lowest MP dose intensity (ie, most likely to be MP intolerant). p value was estimated by using Kruskal-Wallis test. Each box includes data between 25th and 75th percentiles, with a horizontal line indicating the median. Whiskers indicate maximal and minimal observations within 1.5× the length of the box.Reprinted with permission. © 2015 American Society of Clinical Oncology. All rights reserved. Yang, JJ et al: J Clin Oncol Vol. 33, 2015: 1235-1242.