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At the heart of general practice since 1960

new series

cancer in primary care

symptoms and investigations

Fatigue

In this new series, Dr William Hamilton and Professor Debbie Sharp give advice on dealing with non-specific symptoms and tests in primary care – starting with fatigue

Most symptoms of cancer are specific to a single cancer, or at least give a clue as to which body system may be the source of the problem. Thus dysphagia suggests an oesophageal problem, postmenopausal bleeding a uterine problem. Some other symptoms do not have an obvious link to one site.

In addition, these general symptoms of cancer, such as fatigue or weight loss, also frequently occur with benign conditions. So not only has the GP to consider if cancer is a possible diagnosis, they also have to think of where in the body the cancer may be to target initial investigation.

Furthermore, some patients with cancer – especially lung cancer – just feel unwell. This general malaise is impossible to quantify (and difficult for patients to describe, or doctors to classify) but is nevertheless real. Many patients, after their diagnosis is made, are able to say, 'I knew there was something wrong'.

It is not only primary cancers that can share common symptoms. For example, many cancers metastasise to bone and it is not uncommon for the initial presentation to be from the secondary spread to bone rather than from the primary tumour. In some instances, the secondary spread may mimic a primary cancer.

A lung cancer secondary in the brain may present very similarly to a primary brain tumour. Abnormal masses on a chest X-ray may be primary or secondary cancers – indeed, they may be benign.

Fatigue is a very common complaint and encompasses a range of different concepts, from tiredness to the inability to perform one's usual activities. One in five adults report they have experienced tiredness in the previous two weeks, and around 2 per cent of the adult population consult their GP with fatigue in any one year.

In older people, consultation for fatigue is even more common, with 3 per cent of men and 7 per cent of women over 75 visiting their GP in any one year complaining of this symptom. With such high figures in the normal population it is not surprising that the risk of cancer is very low in patients complaining of fatigue.

An elegant Dutch study recorded all malignancies diagnosed after a presentation of fatigue to primary care: in the four years after the symptom was reported to the GP, 3.7 per cent of those with fatigue had developed a malignancy. This sounds high but reflected the age group studied; 3.4 per cent of patients who had not complained of tiredness also developed a malignancy during the same four years.

Of the most common cancers, lung has the strongest association with fatigue. Over a third of patients report fatigue to their GP before diagnosis. Furthermore, a small proportion of lung cancer patients describe isolated fatigue for many months before diagnosis. Colorectal cancer may also present with fatigue, but in most instances it can be explained by the associated anaemia. Many haematological malignancies can cause fatigue; again, this is partly through anaemia.

Cancer risk in patient with fatigue

The risk of cancer in a patient complaining of fatigue, and who has no other features of cancer, is very low. Overall, the risk is a little below 1 per cent for patients under 70; however, most of the patients with cancer will have some other symptom providing a clue to the diagnosis.

In patients over 70, the risk is approximately 2.5 per cent. Many older patients complaining of fatigue will have anaemia as the initial explanation for their symptom, and this will need further investigation.

How long has the fatigue been present?

Again this is only a rough guide. It is probably sensible to differentiate the duration of fatigue into short (up to a week), medium (up to a month) and long (over a month), and to consider cancer more likely with medium- or long-term fatigue. However, this guide may be misleading, with the probable exception of isolated fatigue over six months in duration, which is unlikely to be malignant.

What other symptoms are present?

The differential diagnosis depends on both the duration of fatigue and the associated symptoms. As infections commonly cause short-term fatigue, the GP will initially focus on these. In medium- or long-term fatigue, the GP will consider autoimmune disorders, endocrine disease, chronic infections, alcoholism, sleep problems (such as sleep apnoea) or depression. In most cases, some clue to occult malignancy will emerge, and many of the above can be eliminated.

Most GPs will take a full blood count when investigating fatigue. This may reveal anaemia, raising the possibility of colorectal cancer, or a raised platelet count, hinting at lung cancer. It can be difficult to spot hypothyroidism clinically, so thyroid function testing seems appropriate.

Obviously, any clues about disease in a particular organ should lead to focused investigation. Further investigation of fatigue to uncover cancer seems unnecessary, unless there are other symptoms.

William Hamilton is a senior research fellow at the division of primary care at the University of Bristol

Debbie Sharp is professor of primary health care at the University of Bristol and a part-time GP

This article is an extract from Cancer Diagnosis in Primary Care edited by William Hamilton and Tim J. Peters, ISBN 978-0-443-10367-4, published by Churchill Livingstone Elsevier, January 2007, price £19.99. To order a copy go to www.elsevierhealth.com or phone Elsevier customer services on 01865 474000

investigating fatigue

Questions to ask the patient

• How long has the fatigue been present?

• What other symptoms are present?

Investigation of fatigue without other features

• Full blood count, plus ESR or CRP

• Thyroid function tests

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