Comprehensive Rehabilitation of the Cancer Pain Patient
When it comes to living with cancer, there is good news and bad news. Although patient prognoses have improved over the last decade—with the result being longer life expectancy and remission rates—residual pain and functional deficits often accompany these successes.1 In fact, many of our oncology colleagues and other allied cancer care providers have placed the emphasis of treatment on both remission and advances in minimizing the disease activity, with less emphasis on the aftermath.2 In many ways, these advances have resulted in a greater proportion of cancer pain shifting from an acute to a chronic condition, and represent the sequelae of effective treatments.3
This shift has required cancer pain management programs to borrow from the chronic pain playbook: using an interdisciplinary approach to rehabilitation and pain management. After all, there is no difference anatomically or physiologically, by biochemical substrate, or through mechanisms of nociception between benign or malignant etiologies of pain.4 These etiologies of cancer pain can be nociceptive (somatic and visceral), neuropathic, or mixed; and temporally may represent acute or active disease, subacute, or chronic with palliative care—or in remission with residual effects.
Although pain is considered the fifth vital sign, it still remains undertreated especially among minorities both in institutions and outpatient settings due to poor assessment, deficiencies in patient and/or provider education, regulatory issues, and fear of opioid treatments.5 This series of articles will review current concepts in the compassionate and multidisciplinary treatment of cancer-related pain.
Goals of Treatment
The goals of a comprehensive interdisciplinary cancer pain management program include improved function to improve quality of life (QoL) with maintenance, or resumption, of activity of daily living (Table 1). In the psychosocial realm, the goals of treatment include lessening the sense of suffering, while fostering an internal locus of control—that is, believing that pain can be controlled by factors such as one's attitude, preparation, and effort. This can be accomplished by providing patients with the skills to manage pain on a daily basis using the minimal amount of medications needed to achieve maximal pain relief, thereby limiting side effects in a cost-effective manner. In palliative cancer pain, the emphasis of care primarily may be to reduce pain, and to sustain function.
As a specialist in cancer pain supportive treatments, I should emphasize that the patient's prognosis, and compliance with treatment recommendations, is strongly correlated with his/her satisfaction with pain control. Compliance to the treatment plan can be cost effective in minimizing additional emergency department visits and subsequent hospitalizations due to inadequate pain control. Pain management also improves patient compliance for other recommended treatments.6 In the vast majority of cancer patients (85%), pain can be well palliated using simple, inexpensive, "low technology" oral analgesics. The cancer pain therapy ladder primarily using oral, transdermal, transmucosal, or suppository agents is effective in alleviating cancer-related pain in up to 80% of patients.7
In the remainder of patients, up to 20% will require supplementary interventions to decrease physical pain.8 In a smaller percentage (5% to 10%) of cancer pain patients, invasive anesthetic or neurosurgical interventions may be required.9 These include adjuvant pain medications, alternate routes of opioid administration, antineoplastic therapy, nonpharmacologic approaches, interventional procedures, and surgery. Neurostimulatory techniques, regional analgesia, and neuroablative procedures can provide excellent palliation in selected refractory patients; however, generally, they do not eliminate the need for systemic opioids. Interventional procedures including nerve blocks (peripheral, epidural, selective nerve root, ganglion, plexus, facet, or medial branch blocks) with radiofrequency denervation, and occasionally chemical neurolysis with botulinum toxin,10 have been useful in selected cases of specific pain generators. Sphenopalatine ganglion, for example, is a neurolytic block for pain due to advanced head and neck cancer.11
Other interventions include thoracotomy, intracerebral, and—more commonly—intraspinal12 analgesics. Neuromodulatory procedures include vagal, occipital, or other peripheral nerve stimulation, and spinal cord or brain stimulation. Neuroablative procedures include the creation of lesions in the dorsal root entry zone, cordotomy, myelotomy, tractotomy, hypophysectomy, thalamotomy, and cingulotomy.13
Identifying Pain Generators
The current treatment of cancer has shifted to more conservative care including radiation therapy (RT), chemotherapy (CT), or minimal resection of neoplastic tissue resulting in higher survival rates,13 but with more residual pain in patients (60% of patients).14 Combined CT and RT results in better remission but has a tendency for higher morbidity rates, including acute and chronic toxicity, as well as treatment-related mortality.11 However, even with less reliance on surgery, preserving the organ does not always correlate with preserved function. Minimally invasive surgery improves functional outcomes. Education is required to inform patients that they need to complete the full course of treatment for a complete remission, which involves improving their compliance and satisfaction with care, and minimizing financial barriers.15
A careful evaluation including history, pain description (particularly if it is worsened during sleep), precipitating and alleviating factors, functional deficits, psychological factors, psychosocial history including the patient's beliefs, physical examination, review of previous records, and a general knowledge of the different characterizations of cancer or nonmalignant pain will optimize a comprehensive assessment. Documentation is crucial, and frequent reassessment is necessary to dynamically evaluate the problem, monitor for any interval changes, and responses to therapy. Even without a specific known pain generator, one must treat pain aggressively during diagnostic evaluation to validate symptoms, provide comfort, and improve compliance.13 Unfortunately, only 0.1% of the cancer literature addresses the diagnosis of pain or its management.16 Determining the etiology of pain is the key to appropriate therapy.17 One must first determine whether the pain generator is coming from peripheral tissue or combined with the central nervous system (at least 33% of cancer pain has a neuropathic etiology as a source, which may be found in combination with somatic pain).18 Table 2 lists some of the common sources of cancer-related pain.13
Somatic Pain Etiologies
There are a number of causes of somatic pain in cancer patients. This section highlights some of the most common.