2.4 STATISTICAL ANALYSES
Patient characteristics were summarized by descriptive statistics.
Spearman’s Rank Correlation Coefficient was utilized to examine the
relationship between total weight-based morphine equivalents and tumor
response. Tumor response was assessed by two measurements: tumor volume
ratio (GTV prior to course 1 divided by GTV following course 2) and
Curie score ratio after two cycles of therapy. We studied associations
of demographic variables (age, sex, race) with opioid exposure variables
(total weight-based morphine equivalents), as well as with outcome
variables (tumor volume ratio and Curie score ratio). Because these
associations were found insignificant, multivariate analyses adjusting
for age, sex, and race were not conducted. Statistical analyses were
conducted using SAS software Version 9.4 (SAS Institute, Cary, NC). A
two-sided significance level of P<0.05 was considered
statistically significant.
RESULTS
DESCRIPTION OF PATIENT POPULATION
Forty-two patients were treated with anti-GD2 mAb during the study
period. Three patients were excluded as they had complete surgical
excision prior to course 2. For these patients, tumor volume ratio was
incalculable and response to treatment could not be attributed to
chemotherapy alone. Three additional patients were excluded from
analysis for the following reasons: one did not complete mAb therapy;
one underwent concurrent radiation therapy; and one was intubated,
mechanically ventilated, and sedated with propofol for the period of the
mAb infusion secondary to respiratory failure. Demographic and clinical
characteristics of the remaining 36 patients are shown in Table 1. The
median age was 6 years (interquartile range 4-7). The majority of
patients were male (55.56%), having a median weight of 15.20 kg
(interquartile range 13.05-18.60), of white race (72.22%), and were
initially given morphine (88.89%).
The median total weight-based
morphine equivalent (over 8 days) was 4.71 mg/kg (interquartile range
3.49-7.96). Seventeen patients had a change in treatment to a second
opioid (opioid rotation) at some point during either of the two 4-day
cycles, either for intolerable side effects or lack of analgesic
efficacy of the initial opioid chosen. In this circumstance, the
secondary opioid was converted to morphine equivalent doses and added to
the initial morphine doses to establish an overall opioid consumption in
morphine equivalent doses (mg/kg).