Interventional Pain Therapies

EPIDEMIOLOGY

Approximately 6.35 million new cases of cancer are diagnosed annually worldwide, half of

which originate in developing nationsand 1.04 million occur in the United States

alone.

Mortality is high; one in five deaths in the United States is a result of cancer, which means

about 1400 cancer related deaths per day.

The morbidity is equally concerning up to 50% of patients undergoing treatment of cancer

and up to 90% of patients with advanced cancer have pain.

Most (65%) cancer pain is due to involvement of organic structures by tumor, notably bone,

neural tissue, viscera, and others.

Up to 25% of cancer pain is due to therapy, including chemotherapy, radiotherapy, and

surgery .

And the rest of “cancer pain” is accounted for by common chronic pain syndromes, including

back pain and headaches, which might have been exacerbated by the ongoing growth ortreatment of cancer.

The World Health Organization (WHO) analgesic ladder, is practical, easy to implement,

and has been taught extensively to health professionals.

However, even when the WHO approach is implemented appropriately and aggressively,

10% to 20% of patients do not attain acceptable pain control.

Traditionally, it has been this refractory group of patients that has been considered for

interventional pain management, but the approach of reserving interventional management as a last resort has been called into question.

PATHOPHYSIOLOGY

A mechanistic approach is useful when formulating the initial treatment plan .

Somatic pain is described as a constant, well-localized pain often characterized as

aching, throbbing, sharp, or gnawing.

It tends to be responsive to opioids and nonsteroidal anti-inflammatory drugs (NSAIDs—

cyclooxygenase-2 inhibitors) and amenable to relief by interruption of proximal pathwaysvia neural blockade when indicated.

Visceral pain originates from injury to organs.

This pain is transmitted by fibers that travel along the sympathetic nervous system.

Visceral pain is characteristically vague in distribution and quality and is often described as a

deep, dull, aching, squeezing, or pressure-like sensation.

Visceral involvement often produces referred pain (e.g., shoulder pain of hepatic origin).

Neuropathic pain is defined as pain caused by injury or irritation to some element of the

nervous system.

Examples of neuropathic pain syndromes include tumor growth around nerve structures;

postsurgical pain syndromes such as post-thoracotomy, post-mastectomy, pain induced by

chemotherapeutic agents affecting peripheral nerve structures.

Neuropathic pain is often resistant to standard analgesic therapies and frequently requires an

approach using combinations of opioids, tricyclic antidepressants, anticonvulsants, oral or topical local anesthetics, corticosteroids, N-methyl-d-aspartate (NMDA) blockers, and others.

TREATMENT

The goal of treatment of cancer pain is to relieve the pain by modifying its source, interrupting

its transmission, or modulating its influence at brain or spinal cord sites.

This can be achieved with single therapy or combinations of the following available

modalities:

A. Antineoplastic treatment

B. Pharmacologic management

1. NSAIDs

2. Opioids

3. Adjuvant analgesics

a. Antidepressants

b. Anticonvulsants

c. Oral local anestheticsd. Corticosteroids

4. Interventional pain management

a. Continuous parenteral infusion of opioids

b. Neuraxial analgesia—epidural or intrathecal infusions

c. Vertebroplasty or kyphoplasty

d. Nerve blocks: local anesthetic nerve blocks and neurolytic nerve blocks

e. Spinal cord stimulation, peripheral nerve stimulation, or peripheral

subcutaneous nerve stimulation

INTERVENTIONAL PAIN MANAGEMENT

When a comprehensive trial of pharmacologic therapy fails to provide adequate analgesia or

leads to unacceptable side effects, consideration should be given to alternative

treatments.

CONTINUOUS SUBCUTANEOUS INFUSION OF OPIOIDS

This modality was frequently used in the past and proved to be effective.

INTRAVENOUS INFUSION OF OPIOIDS WITH PATIENT CONTROLLEDANALGESIA DEVICES

INTRATHECAL DRUG DELIVERY

SYSTEMS

Simple Percutaneous Intrathecal Catheter

Tunneled Intrathecal Catheter

Implantable Drug Delivery Systems

With an IDDS, the initial costs are relatively high ($15,000 to $20,000).

INTRATHECAL VERSUS EPIDURAL DRUG DELIVERY

Compared to IT delivery, epidural infusions require a 10-fold greater volume and dose of opioid in

order to diffuse passively across the dura and enter the subarachnoid (IT) space.

This large difference in infusion volumes and doses has a major impact both on cost and the frequency

of drug reservoir changes, which necessitates breaking the system’s sterility more frequently and likely

results in a higher infection rate.

Furthermore, treatment failure is more frequent with the epidural route due to inadvertent catheter

dislodgment and the development of epidural fibrosis which impedes diffusion of drug to the

subarachnoid space.

Pain in a pattern involving specific, consecutive dermatomes may be blocked with local anesthetics with an appropriately positioned epidural catheter.

SPINAL CORD STIMULATION

This technique has been used successfully for refractory neuropathic chronic pain states in

patients with chronic nononcologic pain.

There is a lack of studies evaluating its use for cancer pain states.

We have used it successfully in patients with CRPS type 2, such as those with postsurgical

pain syndromes, chemotherapy-induced peripheral neuropathy, and postradiation

nerve injury.

Patient selection is very important in the cancer population because MRI at this point is

contraindicated after this device is placed and medical oncologists rely on this study to monitor the progress of disease in these patients

Nerve Blocks of the Trigeminal Nerve and Its

BranchesINDICATIONSThe trigeminal nerve is the fifth cranial nerve and has both motor and sensory function.

In addition to innervating the muscles of mastication, it is responsible for sensation over most

of the face.

Neurolytic blockade of the trigeminal ganglion and its branches is indicated for patients with

primary or metastatic head and neck cancer and associated severe pain.

In the setting of cancer-associated pain, neurolytic blocks are most common,

although local anesthetic block with indwelling catheter, thermal and pulsed radiofrequency ablation, and cryoablative techniques have all been described.