Identifying Prevalence of and Risk Factors for Abnormal Urine Drug Tests in Cancer Pain Patients

Context: Opioids have become a mainstay treatment for severe cancer pain. Although opioid prescribing has decreased, opioid mortality continues to rise. Utilizing urine drug tests (UDT) can help monitor medication adherence and identify use of unprescribed or illicit substances.

Objectives: To identify the prevalence of abnormal UDT among oncologic pain patients, associated demographic and clinical factors, and the most common abnormal substances.

Methods: A retrospective chart review of 2472 patients with a cancer diagnosis and documented UDT in a single center was conducted from January 1, 2018 to February 15, 2020. Multivariable analyses were conducted for 10 baseline patient factors on each of the two primary outcomes-illicit drugs excluding tetrahydrocannabinol and amphetamines and detected-not-prescribed.

Results: Of the 2472 patients, 840 patients (34%) had abnormal results. For illicit drugs, the significant factors (incidence rate ratio [95% CI]) were age (45-54 vs. ≥ 65 years: 7.27 [2.27-23.23]), race (black vs. white: 2.99 [1.39-6.42]), smoking status (current vs. former: 2.63 [1.41-4.90]); never vs. former: 0.27 (0.10-0.76), and benzodiazepine use (use vs. no use: 2.06 [1.03-4.12]). For detected-not-prescribed, the significant factors (incidence rate ratio [95% CI]) were race (black vs. white: 1.37 [1.01-1.85]), smoking status (current vs. former: 1.27 [1.00-1.62]); never vs. former: 0.82 (0.67-1.00), log-transformed morphine milligram equivalence (1.04 [1.01-1.07]), and benzodiazepine use (use vs. no use: 1.64 [1.35-1.98]).

Conclusions: This study demonstrates that oncologic pain patients are not a risk-free population for abnormal UDT, thus recommends a UDT with initial opioid prescriptions and annually thereafter, with more frequent tests for patients suspected to be at higher risk for misuse.