45

Pain, 45 (1991) 45-48

6 1991 Elsevier Science Publishers il DONIS

B.V. 0304-3959/91/$03.50

030439599100102N

PAIN 01756

Pain causes in 200 patients

A. Banning, Pain Clinic, Depariment (Received

referred to a multidisciplinary pain clinic P. Sjergren

ofAnaesthes~a, The

9 August

and

Finsen Institute,

1989, revision received

cancer

H. Henriksen Rigshospitalet,

24 September

2100 Copenhagen 0 (Denmark)

1990, accepted

2 October

1990)

Summary

Causes of pain were analysed in 200 patients referred to a specialized cancer pain clinic. Pain caused by tumour growth was found in 158 patients, pain secondary to cancer or its treatment in 116 patients and pain unrelated to cancer in 33 patients. Visceral involvement (74 cases), bone metastases (68 cases), soft tissue invasion (56 cases) and nerve/plexus pressure or infiltration (39 cases) were the most frequent causes of pain due to tumour growth. Myogenic pain (68 cases) was the most frequent cause of secondary pain. The patients presented with a multitude of different combinations of causes of pain, the majority having at least two separate causes. Since pain treatment in cancer patients should be determined by its aetiology, a detailed analysis of the pain condition in each patient should form the basis for a rational therapy. Key words: Cancer _

pain;

Pain mechanisms;

Pain aetiology

Introduction Many patients with cancer suffer meaningless and unnecessary pain due to insufficient pain management. A more liberal approach to the administration of opioids has improved the quality of life for many cancer patients, but studies have shown that some pain types respond poorly to opioid therapy. An individualized treatment approach, including application of different treatment modalities chosen for the individual pain types, is necessary in order to obtain satisfactory pain relief [2,9]. Therefore detailed knowledge of the nature of a pain condition is necessary when planning treatment. Pain in cancer patients may be caused by one or more anatomically separate neoplastic lesions. Other pain conditions may arise secondary to the primary lesions or to antineoplastic treatment. The prevalence of pain in patients with advanced stages of cancer has been the subject of several investigations [3,5,9,11] but few studies have attempted to distinguish between different pain causes [4,9]. The present study was per-

Correspondence to: Gentofte. Denmark.

A.

Banning,

Mosegardsvej

158,

DK-2820

formed in order to gain information about pain causes in patients with advanced cancer referred to a multidisciplinary cancer pain clinic.

Material and method During a 10 month period, 200 patients were referred by departments of medical and surgical oncology to a multidisciplinary cancer pain clinic. We studied 78 men and 122 women of median age 58 years (range 17-85 years). The cancer diagnoses were: breast (55 patients), lung (42 patients), male urogenital (22 patients), female urogenital (20 patients), gastrointestinal (19 patients), head and neck (13 patients), haematological (11 patients), sarcoma (8 patients) and other types (10 patients). At the time of referral, the cancer had already disseminated in 172 patients. Performance status according to Kamofsky’s classification was recorded [l]. The 3 main categories were used. Nineteen were classified in group A (“Able to carry on normal activity and to work. No special care is needed.“), 121 in group B (“Unable to work. Able to live at home, care for most personal needs. Varying degree of assistance needed.“) and 42 in group C (“Unable to care for self. Requires equivalent of institutional

46

TABLE

I

DISTRIBUTION

OF PAIN

CAUSES

IN EACH

CATEGOR\i

No. of patlent?, Purr1 c~uu.vecl h,,

tUmoUr yrowh (15Xprttwm)

Visceral

74

Bone metastasis

68

Soft tissue invasion

56

Nerwjplexua

pressure or

infiltration

39

Local recurrence

14

C‘utanrous infiltration

‘I

Primq

connective tissue cancer

6

CNS metastaslh

6

Other

5

Pun c~~~t~cl~rwr~s .vewndqv

to ccrncer drserrse or treutnmt

My0gUW

6X

Postsurgical

72

Lymphoedema

71

Perlpheral neuropathy

1’)

Joint Involvement

h

Herpes ro\ter

6

Irradiation

6

fibroslh

Phantom hmb

3

Other

4

Pun wnd~rron.s unrehted Lo\c back pain Osteoarthritis Headache Other ~____

to cancer heuse

thoracic viscera. If the visceral tumour wax known to involve the abdominal wall. retroperitoneul tiaaues 01 chest wall soft tissue, the cause of pain was also classIfied as “soft tissue invasion.” “Cutaneous infiltration” was used when pain was caused bv a cutaneous lexion. “Local recurrence” was used when pain was caused h\ relapse of a tumour that had earlier been removed (e.g.. rectum cancer). If patients experienced pain at anatomically different locations but with the same aetiology. e.g.. bone metastasis, only one pain cause was registered.

(116 purrent.r)

Results A pain problem was present in 1X6 patients; 14 patients were referred for psychological problems without any physical pain condition. The distribution of cause of pain, registered in the 3 different categories is shown in Table I. Pain caused by tumour growth was found in 15X patients. Fifty-two different combinations of pain due

(33 purrent.s) 20 : 5 7

or hospital care. Disease may be progressing rapidly.“); 1X were not classified. Registration of survival had been completed in a period of 15 months, by which time 132 patients had died. The median survival time after referral of these patients was 10 weeks (range 0.5-58 weeka). At the patients’ first contact with the pain clinic, the pain causes were classified on the basis of all available clinical and paraclinical data and a thorough physical examination. Three main categories were used: “pain secondary caused by tumour growth, ” “pain conditions to cancer disease or treatment” and “pain conditions unrelated to cancer disease.” The two former categories may require further classification. “Pain caused by lesion tumour growth” was used when the neoplastic caused nociception directly, while “pain secondary to cancer disease or treatment” was used when pain was a consequence of tumour growth or treatment. but neoplastic tissue was not directly involved in the nociceptive process. Within each main category, aetiology was further subclassified (see Table I). In the category “pain caused by tumour growth,” some of the subclassifications may require further description. “Soft tissue invasion” was used when the tumour invaded surrounding soft tissues, not affecting the cutaneous surface. “Visceral pain” was used when pain was caused by tumour growth in abdominal or

“Combinations

of pain causes”

N=186

N=74 N:18

q q

paln secondary to cancer disease or treatment

0

paln unrelated to cancer disease

pan caused by turnour growth

of the 1Xh patwnta with pain. based on the Fig. 1 Dlatrlbution occurrence of pain causes In each of the 3 main categories: (a) pam caused by turnour

growth,

treatment.

(h) pain secondary

to cancer dlxase

and (c) pain unrelated to cancer.

or

to tumour growth were seen, the most frequent being bone metastasis alone (27 patients), visceral pain alone (21 patients), visceral pain and soft tissue invasion (16 patients), bone metastasis and nerve/plexus pressure or infiltration (10 patients). The remaining 48 combinations were each seen in 6 or fewer patients. In 61 patients with pain caused exclusively by tumour growth, 24 had only one cause of pain. In 116 patients with pain conditions secondary to cancer disease or treatment, the most frequent pain causes were myogenic pain (68 patients), lymphoedema (22 patients), scar pain (22 patients) and neuropathy (19 patients). Pain conditions unrelated to cancer disease were found in 33 patients: low back pain (20 patients), clsteoarthritis (7 patients) and headache (5 patients) were the most frequent. Of the 158 patients who had pain caused by tumour growth, 74 patients also had one or more pain conditions secondary to cancer disease or treatment, and 17 patients presented with pain conditions from all 3 categories (Fig. 1). In 28 patients, pain was not caused by tumour growth; 25 of these patients had pain secondary to cancer disease or treatment, alone (18 patients) or combined with pain unrelated to cancer disease or treatment (7 patients). In 3 patients only pain unrelated to cancer disease or treatment was found. When looking at the occurrence of pain conditions from all 3 main categories, we found that 37 patients presented with 1 pain cause, 57 patients with 2, 44 patients with 3 and 48 patients with 4 or more pain causes (Fig. 2).

Discussion .

For many years clinicians have realized that pain in cancer is not a well defined entity. Pain in cancer is often chronic and arises in deeper tissues. Processes and mediators differ depending on nociceptive stimulus and the tissue involved. Information about many of the

Number

Number patlC?ntS

of different pr.patient

pain conditions N=200

of 57 44 37 20 20

14

0

1

2

3

b

4

a4 pal”

Fig. 2. Number

of different

pain causes per patient

Number of condltmns

processes is still incomplete but enough is known to give a multifaceted picture of the mechanisms involved. It is of major importance to be aware of these different pain mechanisms when performing differentiated pain diagnosis and treatment. Few clinical studies have dealt with pain mechanisms and pain causes in cancer. Foley [4] found that 38% of 397 hospitalized cancer patients complained of pain. The pain syndromes were divided into 3 main categories according to aetiology: (a) 78% of the patients had pain caused by tumour invasion or compression of pain-sensitive structures (bone: 50%, nerve: 25%. hollow viscus: 3%); (b) 19% had pain associated with cancer therapy; and (c) 3% had pain unrelated to cancer. In a study of 667 patients referred to a comprehensive cancer centre, Daut and Cleeland [3] found that report of pain experienced in the last 30 days ranged from 75% of patients with metastatic prostate cancer to 14% of patients with non-metastatic disease of the uterine corpus. Of those patients who had non-metastatic disease and pain, only 17% had pain due to their cancer. Of those patients with metastatic disease and pain, 56% had pain due to tumour growth and slightly more than half of these also had pain causes other than cancer. In a study of 100 patients referred for hospice care, Twycross and Fairfield [9] found that 80% of the patients experienced 2 or more (range l-8) anatomically distinct pains. They applied a diagram adding the catepains” to the classification used by gory “associated Foley [4]. Taken together the studies establish that pain involves an increasing percentage of patients as disease progresses. The prevalence of pain varies according to primary site of disease. The majority of patients have multiple mechanisms of pain. The studies mentioned represent samples of hospitalized patients and may thus inflate data on the prevalence of pain in general. Our material represents a group of patients selected from a basic population of patients attending a comprehensive cancer centre. Patients were referred to the pain clinic when specific oncological treatment and conventional analgesic therapy had failed to provide sufficient pain relief. When comparing the results in the present study to the findings of others, certain modifications are necessary since different classifications of pain causes have been used. The classifications presented by Foley and by Twycross of the physical basis of pain in cancer, both include pain associated with direct tumour involvement, pain associated with therapy and pain unrelated to cancer. They have operated with pain syndromes rather than with individual pain causes and each patient could only be classified into one of the three mutually exclusive categories. We have chosen to use a modification of the classification used by Foley and Twycross. On the basis of all

4x

available clinical and paraclinical data and a thorough physical examination. pain causes were also classified into 3 categories. but each patient could have pain causes from more than one category. Hereby we attempted to obtain a classification that could give a more accurate description of pain mechanisms in the individual patient. We believe that this procedure in the hands of experienced investigators provides reliable results. although a small percentage of pain causes may have been classified incorrectly. There are, however. no objective methods to prove the existence of a particular pain cause. In our series, visceral (74 cases). bone (68 cases). soft tissue invasion (56 cases) and nerve/plexus pressure or infiltration (39 cases) accounted for the majority of pain causes due to tumour growth. There is a larger number of patients with visceral pain in our study compared to other studies. This may at least partly be explained by the fact that in this category we have included thoracic and abdominal viscera, while others [4] have only included the latter. Myogenic pain (68 cases) was the most frequent pain cause secondary to cancer disease or treatment. Myogenic pain is known to be a part of pain syndromes in cancer patients frequently occurring in regions close to the tumour [6]. This myogenic pain may have multiple causes, e.g.. imobilisation, tumour produced algesics, central or local reflexes [8.10]. Only 61 patients had the “classical” tumour pain caused exclusively by tumour growth and as few as 24 of these patients had only 1 pain cause. It is important to keep this in mind when planning treatment, but also has implications for research, since it appears that most patients referred to a pain clinic present with complex pain aetiology. Inadequate pain relief in the patients referred to the pain clinic may have been due to the analgesic therapy not “covering” all of the different pain types. Choice of treatment should be based on a thorough analysis of possible pain conditions, and simultaneous application of different treatment modalities is often indicated. Since psychological factors greatly influence the experience of pain, reassuring the patient, when appropriate. that the pain is not a sign of progressing disease may sometimes relieve pain and suffering to a significant extent.

Finally, we would like to comment on the nomenclz ture of pain in patients with cancer. The term “cancer pain” has been widely used. However. due to the complex nature of pain in malignant disease. also amplv demonstrated in the present study. this term represents an oversimplification and appears to be non-opcrational. In conclusion. the presented data illustrate that pain in cancer patients may be due to multiple causes. the individual patient often presenting with a combination of pain causes. Since choice of treatment should hc based on pain aetiology and pain type. a detailed analyGs of the pain condition in each patient should form the basis for rational therapy.

Acknowledgements

The present Cancer Society.

study

was

supported

by the

Danish

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