Pain experienced by lung cancer patients: a review of prevalence, causes and pathophysiology
Introduction
Where possible the main aim of therapy in cancer is cure. Whatever the eventual outcome, symptom control and quality of life are important to patients, families, health care providers and policy makers [1], [2], [3]. Lung cancer is the commonest malignancy worldwide [4], and 80–90% of patients die within 1 year of diagnosis [5]. The predominance of palliative rather than curative treatment in this group implies that symptom relief is of paramount importance to patients with lung cancer. Pain is one of the most feared symptoms and is common: it is estimated to affect 40–90% of patients with malignant disease [6]. Lung cancer can cause pain either locally by invading the parietal pleura, ribs, thoracic spinal cord or brachial plexus, or elsewhere in the body by its propensity to metastasise. In addition, short and long term sequelae of radiotherapy and chemotherapy treatments can also be painful. For these reasons lung cancer is thought to be one of the commonest cancers to cause pain [6], [7], [8], [9]. Detailed knowledge of the epidemiology of pain experienced by patients with lung cancer is vital for comprehensive assessment of treatment outcome and rational planning of healthcare services.
Many studies have been undertaken to assess the prevalence and nature of pain experienced by patients with cancer. Considering these studies in isolation can be problematic. The prevalence of pain in cancer in general varies widely from study to study, and has been calculated to be as low as 5% [10] and as high as 100% [11], [12]. The type and stage of cancer under scrutiny accounts for some of this variability: lung cancer, head and neck cancer and genitourinary cancer have particularly high rates of pain [6], [7], [13], and in general those with advanced cancer are more likely to experience pain than those with early disease [14], [15]. However, four main variables related to the methods of epidemiological studies affect the data generated: study setting, source of information, measurement of point or period prevalence and comprehensiveness of assessment. Each can be defined in numerous ways. Given the methodological diversity employed and the complexity of the experience of pain itself, we believe a systematic review appraising these variables gives a more comprehensive analysis of the epidemiology of pain in lung cancer than any single study considered in isolation. Further, by drawing information together and considering the results of studies in terms of the underlying methodology a review could assess the generalisability of study findings and be a resource for those caring for these patients.
Our aims were:
- 1.
To estimate the prevalence of pain experienced by patients with lung cancer in various settings, and to assess its relative importance compared to other symptoms.
- 2.
To identify whether the following factors: SCLC or NSCLC histological subtype; age; gender; underlying pain aetiology or type of cancer treatment received influence the experience of pain by patients with lung cancer.
- 3.
To ascertain the nature of pain experienced by patients with lung cancer in terms of site; severity; duration and underlying pathophysiology of pain.
Section snippets
Methods
A Medline (1966–June 2002) and Cancerlit (1975–May 2002) search was undertaken using the MeSH headings lung cancer, pain, and cancer pain. The abstracts of all identified studies were reviewed. Studies whose major aims included the exploration of the epidemiology of pain experienced by patients with lung cancer were included. Reference lists were also reviewed to identify further suitable studies. Case reports and intervention studies (whose major aim was the assessment of efficacy of a
Results
The search strategy found 1007 studies. Thirty-two studies whose main aim was the exploration of the epidemiology of pain were identified (Table 1). Two further studies were included: these had main aims other than the assessment of pain, but contained data pertinent to Aim 2 and/or Aim 3 (factors that may affect the experience or development of pain). One study assessed the verbal descriptors of pain patients with lung cancer [17], and the other assessed pain in patients with lung cancer which
Nature of the evidence: methodological limitations and their consequences
This review identified 32 studies of the epidemiology of pain experienced by patients with lung cancer. The methods used were diverse in terms of study setting, sources of information, measurement of point or period prevalence, and comprehensiveness of assessment.
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