Pathological anatomy of cancer pain

[Intractable cancer pain as a reason for referral : Analysis of pain etiology and previous drug treatment.]

Many studies have demonstrated that cancer pain can be relieved in most cases by suitable analgesic medication. Patients with a diagnosis of "intractable cancer pain", however, are referred to our pain clinic nearly every day. A retrospective study of 1140 patients was therefore performed to evaluate the pain mechanisms and whether analgesic pretreatment had been adequate. Half of the patients (53%) were suffering from pain at more than one site. The most frequent locations were the back (36% of the patients), abdomen (30%), and the thoracic (22%) region. The main pain etiologies were compression or infiltration of pain-sensitive structures by the tumor (84% of the patients), and less frequently oncological treatment (18%), debilitating disease (10%), or causes unrelated to tumor or therapy (9%). Pain could be classified with almost equal frequency as neuropathic, visceral, soft tissue-related, or bone-related. Upon admission to our pain clinic, most patients (86%) indicated pain of severe intensity. The principal causes for the inadequacy of the analgesic pretreatment were: failure to prescribe analgesics (10% of the patients), irregular intake schedule or prolonged intervals between applications (66%), underdosage of nonopioid analgesics (27%) or opioids (42%), and withholding of nonopioid analgesics (30%), strong opioids (14%), or co-analgesic drugs (17%), although their prescription was indicated. The severe pain was thus caused in many patients by simple mistakes in the prescription of analgesics. Terms like "intractable" should be used with caution when referring to cancer pain because they are often unreflected and can make patients and physicians feel helpless or insecure.

Pain Control Research in the Terminally ILL

The realities of clinical practice as well as the intricacies of basic science must be taken into account by future research into pain control for the terminally ill. Attention is also needed to the integration of various approaches to pain control in order to develop the best possible treatment plan for each individual. An encouraging development in this regard is the rapid growth of interdisciplinary pain clinics and hospice programs. A review of the research literature also suggests that the politics of pain control is another topic requiring closer attention. As a recent National Institutes of Health conference has found, pain control is often inadequate across all settings: acute pain, chronic non-malignant pain, and pediatric pain. It is necessary not only to make further strides in pain control per se, but also to identify those factors that facilitate or hinder the dissemination and implementation of improved techniques. The two main goals in care of the terminally ill are to optimize the quality of their remaining life and to alleviate the distress of their survivors. Pain control research has contributed significantly to meeting those goals, but continued progress is needed in both basic studies and the expanded application of new techniques.

Integration of pain management into comprehensive cancer care

Pain management is an integral component of comprehensive cancer care. Designing an effective pain control strategy for the individual patient requires knowledge of the ways in which a patient's cancer, cancer therapy, and pain therapy can interact. Two important aspects of cancer that affect the way in which pain is managed are the cancer's treatability and components of its pathophysiology that themselves do not cause pain (the cancer's "nonpain" pathophysiology). Cancer treatability modifies the need for pain management and the appropriateness of invasive pain procedures. Cancer nonpain pathophysiology can interfere with the oral administration of medications, narrow the patient's therapeutic window for analgesic drugs, limit the effectiveness of psychologic pain therapies, and complicate or preclude invasive pain-relieving procedures. In addition, cancer therapy can interfere with or enhance pain therapy and vice versa. Cancer therapy can interfere with pain therapy by causing pain or by producing other adverse effects. Cancer therapy can enhance pain therapy by reducing the extent of cancer, by acting as a coanalgesic, and by providing intravenous access for parenteral drug administration to patients who require it. Pain therapy can interfere with cancer therapy by increasing or complicating the adverse effects of cancer therapy. Pain therapy can enhance cancer therapy by improving patient performance, and certain palliative surgical procedures may have the ancillary effect of improving organ function. Five case descriptions are presented as illustrations of effective integration of pain management into comprehensive cancer care.

Biobehavioral factors in cancer pain

Despite the presence of pathology in cancer pain, the pain experience in adult cancer patients cannot be totally explained by the extent of such pathology. Unlike chronic benign pain very little research on the role of biobehavioral factors has been conducted to help explain this paradox. The literature on the role of biobehavioral factors in the cancer pain experience is reviewed. A brief review of epidemiology and pathophysiology is presented. Following this, the biobehavioral literature was organized according to research on psychological characteristics and environmental factors. Research addressing affective, cognitive, behavioral and physiological reactions to pain was also discussed. Despite the paucity of studies, the review suggested the following: (1) personality factors do not appear to play a consistent role in the modulation of pain in cancer patients; (2) the work on environmental influences on cancer pain indicate a weak association between such factors as social network and pain intensity; (3) studies on affective state indicate minimal relationships to pain, and lastly, (4) studies on cognitive responses to pain in cancer patients and their influence on the pain experience have not been conducted. To date, in the areas where biobehavioral factors have been investigated, the findings appear modest. However, many potential variables, e.g., self-esteem, the role of family, the role of models, past or current work environments, social learning factors and responses to pain such as fear, somatization and reattribution have not been explored with cancer patients. While the influence of biobehavioral factors in adult cancer pain appear to be relatively modest, the literature is not extensive. Increased efforts at more precisely determining the input of such factors in cancer pain are warranted, particularly given the role of such variables in other recurrent and chronic pain states.