CLEVELANDA comprehensive evaluation of acute and chronic pain
in the cancer patient is essential in order to choose the appropriate
therapy, detect the progression of disease, and optimize quality of
life, Donna S. Zhukovsky, MD, of the Harry R. Horvitz Center for
Palliative Medicine at the Cleveland Clinic Foundation, said at a
conference on palliative medicine sponsored by the Cleveland Clinic Foundation.
In addition to a medical history, such an evaluation must include the
patients functional status, as well as social and psychological
factors. Depression, anxiety, loss of financial autonomy, and changes
in the patients role within the family and community can all
affect the perception of pain. Failure to address all
contributing factors will not result in the treatment goal, which is
to optimize the quality of life, Dr. Zhukovsky said.
The importance of proper pain diagnosis and control was shown by a
study of 276 consecutive pain service consultations conducted at
Memorial Sloan-Kettering Cancer Center, Dr. Zhukovsky said. In 64% of
patients, the evaluation identified a previously undiagnosed etiology
for the pain.
There are two basic categories of cancer pain, nociceptive and
neuropathic, Dr. Zhukovsky said. Nociceptive pain can be somatic or
visceral. Somatic pain is well-localized and usually described as
aching, throbbing, and gnawing. It is caused by the activation of
nociceptors in skin and deep tissues, as, for example, when tumor
invades soft tissue.
Visceral pain, by contrast, is poorly localized, she said. Patients
describe deep aching, cramping, and pressure. It is caused when
stretched, distended, or inflamed thoracic or abdominal viscera
activate nociceptors. Referred pain is also visceral pain.
The other category of cancer pain, neuropathic pain, is described as
burning, shooting, stabbing, or vice-like. Patients may say it feels
like bugs crawling on their skin, and they may say they feel like
theyre going crazy. Neuropathic pain is caused by injury to the
peripheral or central nervous system, due to tumor infiltration,
chemotherapy, or radiation. Neuropathic pain is an unfamiliar
experience for most people.
Neuropathic pain is generally difficult to treat well, she said. It
may be less opioid responsive than nociceptive pain. Adjuvant agents,
like antidepressant drugs or anticonvulsants, play a main role in its
treatment, Dr. Zhukovsky said.
Most cancer patients require several modalities of pain control.
These include disease-specific therapy, drugs, physical therapy, and
cognitive-behavioral therapy. For a small group of patients, invasive
anesthetic and surgical techniques of pain control may be extremely
beneficial, she said. Transcutaneous electrical nerve stimulation
(TENS), a noninvasive technique of neuroaugmentation that involves a
battery-powered generator applied to the skin, has proven useful for
There are three classes of pharmacologics for treating pain:
nonopioids (acetaminophen, aspirin, and other nonsteroidal anti-inflammatories),
opioids, and adjuvant analgesics, Dr. Zhukovsky said. Pharmacologics
should be administered following a few basic principles, she said.
First, believe the patients complaint of pain. The literature
shows that physicians tend to underestimate the patients degree
of pain, she said. Perform a complete evaluation.
When prescribing, start with one drug at a time and allow an adequate
trial before deciding the drug is ineffective (see description of the
WHO ladder below).
Choose the appropriate route of administration, she said. Although
oral administration is preferred, it may not be feasible. Routes of
drug administration include oral, rectal, sublingual, parenteral,
spinal (epidural, intrathecal), trans-dermal, and transbuccal.
Provide regularly scheduled drug administration for chronic pain and
supplemental or rescue doses for breakthrough pain.
Anticipate and treat side effects. When starting an around-the-clock
opioid regimen, for instance, expect constipation and start a bowel
regimen as well. Continuously assess pain control to note any
Finally, remain readily available to the patient.
The WHO Ladder
When prescribing pain control, clinicians should follow the World
Health Organization three-step analgesic ladder, which allows for the
sequential use of progressively stronger analgesic agents, in
combination with adjuvant therapies if indicated. You can start
on whatever step is needed, she said.
In step 1, a nonopioid is used. If this does not relieve the pain, an
opioid for mild to moderate pain should be added (step 2). If this
combination strategy fails, an opioid for moderate to severe pain
should be substituted, with nonopioid and adjuvant therapies
continued if appropriate (step 3).
Only one drug from each of the groups should be used at the same
time. If a step 2 opioid ceases to be effective for the patient, the
clinician should prescribe a stronger agent rather than switch to an
alternative step 2 drug.
Use of Opioids
The nonopioids, unlike opioids, all have a ceiling effect. After a
certain point, if the dose is increased, no additional analgesia is
obtained but side effects worsen. When combination drugs such as
Percocet (oxycodone and acetaminophen) are used, the nonopioid
component limits dose escalation.
Opioid dosages, on the other hand, can be increased as needed.
Patients may ask if they are receiving a high dose, Dr. Zhukovsky
said. Remind patients that numbers dont matter, she
said. The right dose is the one that adequately controls pain.
Some clinicians may be surprised to learn that parenteral infusion of
opioids is quite feasible even with home care. Use a 25-gauge needle
under the skin on the chest or belly, Dr. Zhukovsky said. There are
some volume constraints with this mode of administration.
Rescue doses, used for breakthrough pain, may be needed up to four
times a day even in patients with well-controlled pain, she noted.
Side effects of opioids include constipation, sedation, and altered
mental status, nausea and vomiting, orthostatic hypotension, and dry
mouth. Except for constipation, patients rapidly develop tolerance to
these side effects. Preventing dry mouth may be particularly
problematic, she said. Meticulous mouth care is important.
Sucking on ice chips may also help.
Morphine is the standard used for comparison among different opioid
analgesics. However, its good to have a variety of
opioids to handle patients with various side effects, Dr.
Codeine, which metabolizes to morphine, is more nauseating and
constipating than morphine. Heroin, although available for medicinal
use in the United Kingdom and Canada, is unavailable in the United
States. Around-the-clock use of meperidine is contraindicated, since
it leads to the accumulation of norme-peridine, a toxic metabolite.
Clinicians can use the phenomenon of cross-tolerance to better manage
sedation and nausea and vomiting in patients receiving opioid
therapy, she said. By alternating opioids, the patient receives the
benefit of analgesia with fewer side effects. The alternate opioid
should be given at half the equianalgesic dose, Dr. Zhukovsky said.
She noted that nausea and vomiting may also be helped by switching
modes of administration or by administering an antiemetic.
Opioid-related sedation can also be helped by opioid rotation or by
administration of a stimulant such as methylphenidate, she added.