What are the different types of pain, and how should they inform clinicians’ understanding about what approaches might work for managing their patients in pain?
The way the central nervous system responds to pain is analogous to the loudness of an electric guitar. You can make an electric guitar louder either by strumming the strings harder or by turning up the amplifier. For many people with fibromyalgia, low back pain, and endometriosis, for example, the problem is really more that the amplifier is turned up too high rather than its being that the guitar is strummed too strongly. That kind of pain where the pain is not due to anatomic damage or inflammation is particularly flummoxing for providers.
Can you explain the design of the new study?
It’s a 13-site study looking at four treatments: enhanced self-care, cognitive-behavioral therapy, physical therapy, and duloxetine. It’s a big precision medicine trial, trying to take everything we’ve learned and putting it all into one big study.
We’re using a SMART design, which randomizes people to two of those treatments, unless they are very much improved from the first treatment. To be eligible for the trial, you have to be able to be randomized to three of the four treatments, and people can’t choose which of the four they get.
We give them one of those treatments for 12 weeks, and at the end of 12 weeks we make the call – “Did you respond or not respond?” – and then we go back to the phenotypic data we collected at the beginning of that trial and say, “What information at baseline that we collected predicts that someone is going to respond better to duloxetine or worse to duloxetine?” And then we create the phenotype that responds best to each of those four treatments.
None of our treatments works so well that someone doesn’t end up getting randomized to a second treatment. About 85% of people so far need a second treatment because they still have enough pain that they want more relief. But the nice thing about that is we’ve already done all the functional brain imaging and all these really expensive and time-consuming things.
We’re hoping to have around 700-800 people total in this trial, which means that around 170 people will get randomized to each of the four initial treatments. No one’s ever done a study that has functional brain imaging and all these other things in it with more than 80 or 100 people. The scale of this is totally unprecedented.
Given that the individual therapies don’t appear to be all that successful on their own, what is your goal?
The primary aim is to match the phenotypic characteristics of a patient with chronic low back pain with treatment response to each of these four treatments. So at the end, we can give clinicians information on which of the patients is going to respond to physical therapy, for instance.
Right now, about one out of three people respond to most treatments for pain. We think by doing a trial like this, we can take treatments that work in one out of three people and make them work in one out of two or two out of three people just by using them in the right people.