CHICAGO – The antidepressant duloxetine reduces chronic pain from chemotherapy-induced peripheral neuropathy with fewer side effects than with current therapies, according to results of a phase III, double-blind trial.
Among evaluable patients, 59% reported less pain with duloxetine (Cymbalta), compared with 38% with placebo. A pain reduction of 30% or more – a measure considered clinically significant – was reported by 33% and 17%, respectively.
"Duloxetine 60 mg a day is the first drug to be shown to be effective in painful chemotherapy-induced peripheral neuropathy based on the results of a randomized trial," Ellen Lavoie Smith, Ph.D., said at a press conference at the annual meeting of the American Society of Clinical Oncology.
A variety of other agents – including gabapentin and tricyclic antidepressants – have been shown to be effective in treating neuropathic pain and are routinely pressed into service in oncology practice, but have failed to demonstrate efficacy in randomized trials of peripheral neuropathy caused by chemotherapy, she noted.
Dr. Ellen Lavoie Smith
"Some patients endure this painful neuropathy for months and possibly for as long as years following completion of chemotherapy," she said. "It’s chronic, it’s very distressing and it’s disabling. And there is nothing to date effective in treating this problem."
Duloxetine is approved to treat major depressive disorder, with an additional indication for chronic musculoskeletal pain added in 2010. The safety label was revised in September 2011 to include warnings for severe skin reactions including Stevens-Johnson Syndrome and erythema multiforme.
The Cancer and Leukemia Group B (CALGB) 170601 trial randomized 231 patients with painful neuropathy after receiving single-agent paclitaxel (Taxol) or oxaliplatin (Eloxatin) chemotherapy to duloxetine 30 mg for 1 week and 60 mg for 4 weeks, followed by crossover to placebo after a 1-week washout period or the same regimen in the opposite order. Pain levels were assessed weekly using the Brief Pain Inventory-Short Form (BPI-SF) in 220 patients.
The average change in BPI-SF score, the study’s primary outcome, was -1.09 in patients given duloxetine, compared with –0.33 given placebo (P = .003), reported Dr. Smith, with the University of Michigan, Ann Arbor.
During duloxetine treatment, patients also experienced a significant reduction in the BPI-SF pain interference score, a sum of seven items including interference with general activity, mood, walking, normal work, relations with people, sleep and enjoyment of life. There was no difference in duloxetine efficacy based on the specific neurotoxic chemotherapeutic agent received.
In all, 21% of patients said their pain was cut by at least one-half with duloxetine, while only 9% taking placebo did.
Interestingly, 11% of patients saw their pain increase with the serotonin-norepinephrine reuptake inhibitor, compared with 28% with placebo. The reason for the finding is unclear, Dr. Smith said in an interview.
"Pain is a very complicated thing to study," she said. "There are many things that go into it – psychosocial issues, environmental issues, cultural issues, but again, there may be patients who are more likely to respond to these drugs because their central nervous system isn’t really working normally."
Overall, duloxetine was well tolerated, but was associated with significantly more grade 2 or greater fatigue than placebo (11% vs. 3%; P = .029). Dr. Smith pointed out that the overall incidence of side effects was lower than observed in two studies of diabetes-related peripheral neuropathy, likely because they used the 60 mg dose without the lower 30 mg starting dose.
Dr. Hope Rugo, an oncologist at the University of California, San Francisco, who was not involved in the study, said one of the advantages of duloxetine is the lack of somnolence observed in the study – a side effect that is bothersome to many of her breast cancer patients taking gabapentin for chronic neuropathic pain induced by taxanes or platinum-based therapy.
Press briefing moderator Dr. Nicholas Vogelzang, head of genitourinary cancer at the Nevada Cancer Institute in Las Vegas, echoed those remarks and said that neuropathy is fairly common among his patients treated with platinum-based chemotherapy. Duloxetine is an addition to the oncologist’s armamentarium, he said, adding "I’m certainly going to use this when I get back to the office."
Dr. Smith acknowledged that not everyone responded to duloxetine, but said that the dual serotonin norepinephrine reuptake inhibitor improves compliance with chemotherapy treatment and that most patients saw improved function and quality of life.
Patients with depression were excluded from the trial, so the effect of duloxetine was not simply because of improved mood, she said. Instead, it is thought that the drug eases pain by increasing serotonin and norepinephrine, and that responders may have an abnormality in the way their brain processes pain because of lower levels of these two pain-inhibiting neurotransmitters. Future work will try to determine which patients are most likely to respond to the antidepressant.