Will This Trial Solve Chronic Back Pain?

Daniel Clauw, MD


August 01, 2023

Daniel Clauw, MD

Chronic pain, and back pain in particular, is among the most frequent concerns for patients in the primary care setting. Roughly 8% of adults in the United States say they suffer from chronic low back pain, and many of them say the pain is significant enough to impair their ability to move, work, and otherwise enjoy life. All this, despite decades of research and countless millions in funding to find the optimal approach to treating chronic pain.

As the United States crawls out of the opioid epidemic, a group of pain specialists is hoping to identify effective, personalized approaches to managing back pain. Daniel Clauw, MD, of the University of Michigan, is helping lead the BEST trial. With projected enrolment of nearly 800 patients, BEST will be the largest federally funded clinical trial of interventions to treat chronic low back pain.

Medscape Medical News spoke with Clauw — a professor of anesthesiology, internal medicine, and psychiatry — about the ongoing trial, and the state of research into chronic pain generally. This interview has been edited for length and clarity.

What are your thoughts on the current state of primary care physicians' understanding and management of pain?

Primary care physicians need a lot of help in demystifying the diagnosis and treatment of any kind of pain, but back pain is a really good place to start. When it comes to back pain, most primary care physicians are not any more knowledgeable than a layperson.

What has the opioid debacle-cum-tragedy taught you about pain management, particular as regards people with chronic pain?

I don't feel opioids should ever be used to treat chronic low back pain. The few long-term studies that have been performed using opioids for longer than 3 months suggest that they often make pain worse rather than just failing to make pain better — and we know they are associated with a significantly increased all-cause mortality with increased deaths from myocardial infarction, accidents, and suicides, in addition to overdose.

Given how many patients experience back pain, how did we come to the point at which primary care physicians are so ill equipped?

We've had terrible pain curricula in medical schools. To give you an example: I'm one of the leading pain experts in the world and I'm not allowed to teach our medical students their pain curriculum. The students learn about neurophysiology and the anatomy of the nerves, not what's relevant in pain.

This is notorious in medical school: Curricula are almost impossible to modify and change. So it starts with poor training in medical school. And then, regardless of what education they do or don't get in medical school, a lot of their education about pain management is through our residencies — mainly in inpatient settings, where you're really seeing the management of acute pain and not the management of chronic pain.

People get more accustomed to managing acute pain, where opioids are a reasonable option. It's just that when you start managing subacute or chronic pain, opioids don't work as well.

The other big problem is that historically, most people trained in medicine think that if you have pain in your elbow, there's got to be something wrong in your elbow. This third mechanism of pain, central sensitization or nociplastic pain — the kind of pain that we see in fibromyalgia, headache, and low back pain, where the pain is coming from the brain — that's confusing to people. People can have pain without any damage or inflammation to that region of the body.

Physicians are trained that if there's pain, there's something wrong and we have to do surgery or there's been some trauma. Most chronic pain is none of that. There's a big disconnect between how people are trained, and then when they go out and are seeing a tremendous number of people with chronic pain.

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 it being that the guitar is being 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 tell us about 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 put 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 1 out of 3 people respond to most treatments for pain. We think by doing a trial like this, we can take treatments that work in 1 out of 3 people and make them work in 1 out of 2 or 2 out of 3 people just by using them in the right people.

How do you differentiate between these types of pain in your study?

We phenotype people by asking them a number of questions. We also do brain imaging, look at their back with MRI, test biomechanics, and then give them four different treatments that we know work in groups of people with low back pain.

We think one of the first parts of the phenotype is, do they have pain just in their back? Or do they have pain in their back plus a lot of other body regions? Because the more body regions that people have pain in, the more likely it is that this is an amplifier problem rather than a guitar problem.

Treatments like physical therapy, surgery, and injections are going to work better for people in whom the pain is a guitar problem rather than an amplifier problem. And drugs like duloxetine, which works in the brain, and cognitive-behavioral therapy are going to work a lot better in the people with pain in multiple sites besides the back.

To pick up on your metaphor, do any symptoms help clinicians differentiate between the guitar and the amplifier?

Sleep problems, fatigue, memory problems, and mood problems are common in patients with chronic pain and are more common with amplifier pain. Because again, those are all central nervous system problems. And so we see that the people that have anxiety, depression, and a lot of distress are more likely to have this kind of pain.

Does medical imaging help?

There's a terrible relationship between what you see on an MRI of the back and whether someone has pain or how severe the pain is going to be. There's always going to be individuals that have a lot of anatomic damage that don't have any pain because they happen to be on the other end of the continuum from fibromyalgia; they're actually pain-insensitive people.

What are your thoughts about ketamine as a possible treatment for chronic pain?

I have a mentee who's doing a ketamine trial. We're doing psilocybin trials in patients with fibromyalgia. Ketamine is such a dirty drug; it has so many different mechanisms of action. It does have some psychedelic effects, but it also is an NMDA blocker. It really has so many different effects.

I think it's being thrown around like water in settings where we don't yet know it to be efficacious. Even the data in treatment-refractory depression are pretty weak, but we're so desperate to do something for those patients. If you're trying to harness the psychedelic properties of ketamine, I think there's other psychedelics that are a lot more interesting, which is why we're using psilocybin for a subset of patients. Most of us in the pain field think that the psychedelics will work best for the people with chronic pain who have a lot of comorbid psychiatric illness, especially the ones with a lot of trauma. These drugs will allow us therapeutically to get at a lot of these patients with the side-by-side psychotherapy that's being done as people are getting care in the medicalized setting.

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