2.2. Study Outcomes
The primary outcome of this study evaluated the percentage of time
within therapeutic ANC range (defined as 500 – 1,500/μL) in the
allopurinol cohort, with a comparison of values pre-initiation of
allopurinol and post-initiation of allopurinol. ANC values were
collected for all patients from the start of maintenance until the end
of maintenance or May 31, 2022, whichever came first. Secondary
endpoints included a comparison of the percentage of time within
therapeutic ANC range between the allopurinol cohort and the standard
treatment cohort, as well as the change in 6MMP:6TGN metabolite ratios
within the allopurinol cohort compared to the standard treatment cohort.
The resolution of hepatotoxicity, GI symptoms, rash, and hypoglycemia in
the allopurinol cohort were also evaluated. All metabolite values
obtained during maintenance therapy were collected for each patient.
Patients in the allopurinol cohort with hepatotoxicity as a rationale
for either metabolite collection or allopurinol initiation had AST, ALT,
total bilirubin, and direct bilirubin values collected from the
initiation of allopurinol, and for the 12 weeks following. Resolution of
hepatotoxicity was defined as AST and ALT values less than 5x ULN and/or
total bilirubin and direct bilirubin within normal limits at 12 weeks
post allopurinol initiation. GI symptoms, rash, and hypoglycemia data
were all obtained through provider progress notes. Resolution of GI
symptoms, rash, and hypoglycemia were defined as subjective improvement
based on provider notes at 12 weeks post allopurinol initiation.
Descriptive dosing characteristics of allopurinol and 6MP post
allopurinol initiation were collected.