Evaluating the risk of methadone and QTc interval prolongation in an oncologic population

BACKGROUND: Methadone is commonly used as an alternative to other opioids for managing cancer-related pain. High-dose methadone, primarily in opioid dependence treatment, has been associated with QTc prolongation and dangerous arrhythmias. The cardiovascular effects of methadone at lower doses, as used in cancer pain management, remain less well characterized. METHODS: We conducted a retrospective chart review of 492 adult patients who received methadone for cancer-related pain management. For each patient, we collected demographic and clinical data, including age, sex, cancer diagnosis, initial methadone dosage, adjuvant medications, and comorbidities. QTc interval measurements were extracted from ECGs performed at baseline (within 12 months prior to methadone initiation) and at follow-up intervals of 0-6 months, 6-12 months, and ≥12 months after initiation. RESULTS: The linear mixed-effects model shows a statistically significant increase in QTc interval by 4.36 ms at ≥12 months after methadone initiation. The prevalence of cardiac comorbidities was associated with a statistically significant increase in QTc by 9.40 ms. No other timeframe, demographic characteristic, or clinical characteristic that we investigated was associated with a statistically significant change in QTc. The overall proportion of patients with QTc prolongation increased modestly from 3% at baseline to 6.8% after 12 months following the initiation of methadone. CONCLUSION: In this large retrospective cohort of oncology patients receiving methadone for pain management, methadone was associated with a small but statistically significant increase in QTc interval ≥12 months after starting therapy, with a mean increase of approximately 4 ms. This magnitude of QTc change is unlikely to produce meaningful clinical manifestations for most patients. These findings support the low risk of QTc prolongation for most patients with cancer taking methadone and encourage a risk-stratified approach to methadone use in cancer pain with targeted ECG monitoring regimens for patients with elevated baseline QTc or underlying cardiac disease.