Before initiating an analgesic plan, clinicians should determine if the pain etiology is related to the cancer or a nonmalignant etiology.
The thoracic spine is the most common area of spinal metastatic disease: the most frequent cancers are breast, lung, prostate, thyroid, and renal. Cancer-related back pain often worsens at night, does not improve with rest or lying down, and progresses with time.

Nearly 25% of the population experience low back pain (LBP) in any given year, with a lifetime prevalence of up to 85%. Even among cancer populations, a significant amount of LBP have nonmalignant causes.

Common nonmalignant causes of back pain
Many nonmalignant back pain syndromes are clinical diagnosis where history and physical examination (PE) guide the diagnosis and treatment without the need for radiologic imaging. Conservative management (e.g., rest, stretching, heating pads, physical therapy, anti-inflammatory medications, anti-epileptics, or antidepressants) is usually effective.
This contrasts with malignant causes of back pain that very frequently require radiologic imaging, since the tissue destruction associated with spinal tumors worsens over time unless the underlying cancer is treated (e.g., radiation therapy or systemic cancer treatment).

• Sacroiliac (SI) dysfunction is an L-shaped articulation between the sacrum and ilium. Pain is caused by hyper/hypomobile joints or repetitive loads contributing to misalignment. Clinical presentation often involves acute or gradual one-sided pain in the back, buttock, or groin with SI joint tenderness. Pain radiation into the ipsilateral extremity is common. Neurologic deficits are uncommon. Rest, nonsteroidal inflammatory medications (NSAIDS), and physical therapy are often effective treatments. If pain control is inadequate, consider injection of steroid and a local anesthetic into the SI joint under image ultrasound or fluoroscopic guidance.

• Vertebral compression fractures can result from osteoporosis or trauma; they are often diagnosed via X-ray imaging. Common history includes a specific area of pain that may or may not include radiation into the extremities. Patients usually describe a specific area of pain or tenderness over a vertebra with an onset that range from being insidious to acute.

• Facet arthropathy. Facet joints are small articulating joints that limit motion and keep the posterior spine in alignment. These joints can wear down and put pressure on the spinal cord, resulting in back pain without neurologic deficits or radiation that is exacerbated by rotation or extension. It can be difficult to distinguish facet arthropathy from discogenic pain. Treatments include physical therapy, a short course of anti-inflammatories, and/or skeletal muscle relaxants. Consider steroid injection or radiofrequency ablation of the medial branch of the dorsal rami at the affected vertebrae for refractory symptoms.

• Discogenic. This pain is caused by degeneration of intervertebral discs. Flexion, sitting, coughing, or Valsalva maneuvers usually worsen the pain. Neurologic deficits are possible if the nerve root is affected, leading to ipsilateral leg or arm numbness, tingling, pain, and/or less commonly weakness. Degenerative disc changes are often associated with facet arthropathy and spinal stenosis, creating diagnostic overlap. Treatments include physical therapy, NSAIDs, acetaminophen, and neuropathic agents. Consider discectomy and spinal fusion surgery in refractory cases with neurologic symptoms.

• Lumbar radiculopathy. Any condition that affects a lumbar nerve root can cause lumbar radiculopathy, the most common of which is lumbar disc herniation. Symptoms vary, but usually present as pain, numbness, tingling, and/or weakness radiating into the legs following a dermatomal distribution: most common location is L4-5 and L5-S1. Treatment includes anti-inflammatories, neuropathic agents, and epidural steroid injections. Consider neurosurgical referral with the presence of focal motor weakness.

• Lumbar spinal stenosis. Degenerative changes in the spine can cause narrowing of the spinal canal and neural structures, most commonly in patients over 50 years old. It is an insidious process with neurogenic claudication, pain in the bilateral buttocks, thigh, or leg with standing or walking that is relieved with sitting or leaning forward (spine flexion), usually manifests as numbness and weakness over the affected spinal segments. Treatment is similar to lumbar radiculopathy.

• Muscle strain/sprain. Self-resolving muscle aches with associated spasm and guarding after an abrupt increase in activity (overuse) and a normal neurologic examination.

See reference for more information.

Adapted from Spickler M, Smith S. Common Non-malignant Causes of Low Back Pain in Patients with Serious Illness. Palliative Care Network of Wisconsin. Fast facts and concepts #431. Internet. Available at https://www.mypcnow.org/fast-fact/common-non-malignant-causes-of-low-back-pain-in-patients-with-serious-illness/. Accessed on October 18, 2021,