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).