Pain Management in Cancer Patients
First in a series of articles about pain management techniques at RGHS.
By Calvin Chiang, MD
Approximately one million patients are diagnosed with cancer each year, with pain being among their most common symptoms. Up to 90 percent of patients with advanced cancer have significant pain, making pain management a challenge for practitioners.
A gamut of etiologies can cause or contribute to pain. It may be due to inflammatory response or mass effect from the primary or metastatic lesions, or from hypercalcemia or other neuroendocrine effects. Lesions can also cause radicular pain: patients with breast, lung and prostate malignancies frequently develop mets to the thoracic spine, resulting in local back pain or radicular pain. Severe neuropathic pain may also be secondary to treatment from chemotherapy, such as plant alkaloids (vincristine/ vinblastine), platinum-based drugs (carboplatin), taxenes or epothilones. Pain can also be due to other treatments, including post-surgical pain and radiation-induced etiologies.
Clearly, cancer pain needs to be treated aggressively, particularly for those who have more aggressive and life-limiting diseases. “Step therapy,” advocated by the World Health Organization, includes initial use of Tylenol and nonsteroidal anti-inflammatory agents, which are particularly beneficial in patients with bone metastases. These medications tend to be forgotten when “moving up the ladder” to opioid therapy, which remains the mainstay of cancer pain therapy. Short acting opioids are initially used, but eventually short and long acting agents may be needed for around-the-clock pain relief.
Opioid therapy may not be as effective for conditions such as neuropathic pain, resulting in heroic doses and significant side effects that may limit effective use. Patients become tolerant to most side effects, including sedation, pruritis, and respiratory depression, but not to constipation due to reduced motility from opioid receptors in the gut. Simple bowel regimens can manage constipation, but resistant symptoms may require treatment such as opioid taper or methylnaltrexone, given SQ, to produce rescue bowel movements. Unfortunately, recent studies suggest that cellular immune suppression due to opioid therapy may potentially stimulate cancer cell growth.
Other medication therapies may include neuromodulators such as gabapentin, Lyrica, or Cymbalta. Gabapentin and Lyrica, also used as anti-seizure drugs, are calcium channel blockers; Cymbalta is a nonspecific reuptake inhibitor, with the noradrenergic contribution. Tramadol and Tapentadol are reuptake inhibitors that may be more efficacious for neuropathic pain. Tricyclic antidepressants are also utilized, with an additional potential benefit of improving sleep hygiene.
At the Center for Pain Management, injection therapy using steroids and local anesthetics may provide pain relief for two to three months. Epidurals and peripheral nerve blocks are used for radicular pain and nerve related pain. Sympathetic blocks such as celiac plexus or ganglion impar injections may help manage abdominal pain and pelvic pain. Longer duration of pain relief – up to 6 months - may be obtained via chemical or radiofrequency neurolysis.
For those patients in whom high-dose opioid therapy is limited by side effects, intrathecal and epidural pumps may be beneficial. Pumps also allow infusion of local anesthetics or other medications, which tends to reduce the overall opioid dose.
Calvin Chiang, MD, is Medical Director of the RGHS Center for Pain Management.