Ketamine as a Novel Solution for Opioid-Refractory Pain in Radiation Necrosis

We present the case of a 36-year-old female with recurrent metastatic melanoma, complicated by radiation necrosis of the left distal thigh musculature, who presented with intractable, debilitating pain approximately seven months following completion of local radiation therapy. Palliative Medicine was consulted for assistance with pain management. Prior to admission, the patient had failed to respond to escalating doses of oral oxycodone and transdermal fentanyl, given in conjunction with a multimodal regimen including acetaminophen, baclofen, celecoxib, duloxetine, and pregabalin. Just before presentation, the patient completed a prednisone taper for treatment of immune checkpoint inhibitor colitis, with suspicion that steroids were likely masking or partially treating pain before discontinuation. She was not a candidate for steroid re-initiation due to upcoming plans for tumor-infiltrating lymphocyte therapy. Despite escalating opioid dosing (up to oral morphine equivalent (OME) 598.75 mg), our patient continued to experience uncontrolled pain along with progressive sedation. We started her on ketamine 0.1 mg/kg/hr and titrated this over the next 24 hours to a final dose of 0.3 mg/kg/hr, which was then continued for 48 additional hours. Following completion of a three-day ketamine infusion, the patient's OME was reduced by 45% to 327.5 mg. In the months following hospital discharge, the patient was subsequently weaned off long-acting opioids and was able to return to her baseline functional status. No previous cases have been reported of the use of ketamine for the treatment of opioid-refractory pain secondary to radiation necrosis. In this case, we have demonstrated ketamine infusion as a successful treatment strategy for reducing our patient's opioid requirement, optimizing pain control, and helping to improve functional status and quality of life.