Chronic pain in survivors: How we can better understand an under-studied problem
Chronic pain in pediatric cancer survivors is one area that needs our help now more than ever.
Chronic pain typically persists past when we would expect normal healing time to end. Unlike acute pain, such as the pain you experience when you break your arm, get a needle stick, or stub your toe on the coffee table, chronic pain lasts for months—even years.
Understudied and overlooked
Chronic pain might initially seem outside the realm of childhood cancer and survivorship, but children undergoing cancer treatments frequently experience pain. In fact, many children also describe pain as the most distressing part of their cancer experience.
Pain can also persist long after cancer treatment has ended. In the journal PAIN, my colleagues and I reviewed research that examined chronic pain among survivors of childhood cancer who were five or more years post-diagnosis. In comparison with other late effects commonly experienced by survivors following treatment completion, we noticed chronic pain had been under-studied.
Given the lack of research on pain among survivors of childhood cancer, we extended our survey of pain research to related populations (pediatric chronic non-cancer pain and pain in adult-onset cancer survivors) to answer an important question: What leads to the development and maintenance of chronic pain among pediatric and adult survivors of childhood cancer?
Where is it coming from?
Sometimes pain is due to procedures such as blood draws or bone marrow aspirations. Other times, it is due to the cancer treatments themselves, such as surgery or chemotherapy. Sometimes it is due to a combination of these factors. And sometimes, it is difficult to determine the exact cause of the pain.
This is because pain is different. It is not like a lot of the other symptoms or conditions we study and treat in medicine. A blood test or scan cannot identify whether pain is present, nor how strongly a person may feel this pain. Pain eludes our typical assessment approaches.
This is largely because pain is a perception. You and I may experience the exact same painful event (such as touching a hot stove), but how I perceive this experience may be different from how you perceive it. As a perception, pain is deeply influenced by psychological, biological and social factors that are unique to each of us. In sum, pain is different and complex.
Let’s assess childhood chronic pain
In our review, the percentage of childhood cancer survivors affected by pain ranged from 5–59%, and measurement approaches varied widely among these studies. When pain was reported, often only its presence or absence was assessed. These limitations to assessment are important, as they may have led us to underestimate the prevalence and impact of chronic pain among survivors. It also wasn’t clear whether survivors experienced more pain than did control groups of individuals with no history of cancer. Of particular concern, survivors who reported pain were more likely to report emotional distress.
We proposed a model that shows potential pathways to pain in survivors of childhood cancer. From diagnosis to survivorship, key developmental, treatment and procedure and health-related factors emerge and contribute to chronic pain. For example, we know that children’s pain memories predict pain they experience several months later. It is therefore likely that negative memories of pain during cancer contribute to the persistence of pain into survivorship. The number of painful procedures and surgeries faced by children during cancer treatment, as well as less-than-ideal management of pain during these events, likely also influence whether survivors develop chronic pain. Finally, we also know that as survivors age, many must manage multiple chronic health conditions involving pain, which could further compound their overall pain levels and self-management.
The bigger picture of chronic pain
In the future, pain researchers will need to include more comprehensive assessments of chronic pain among survivors, longitudinal designs to track the pain of patients and survivors over time, and intervention studies to test the effectiveness of different treatments to reduce pain.
We have just launched a smartphone app-based study to help us answer key questions about chronic pain among survivors. This app will be used in conjunction with the Childhood Cancer Survivor Study, a multi-institutional study whose principal investigator is Greg Armstrong, MD, of St. Jude Epidemiology and Cancer Control. Our data will be a first step in addressing the many gaps and limitations in chronic pain and survivorship research. Specfiically, we want to hone in on the prevalence rate and learn more about why some survivors develop chronic pain and others do not.
At St. Jude, I have the honor and privilege to, as Danny Thomas said, do for others: As a researcher, to better understand chronic pain in the context of childhood cancer and survivorship; and as a clinician, to help patients and survivors effectively manage pain while living their lives to the fullest.