When should unexpected weight loss warrant further investigation to exclude cancer?

What you need to know

• Unexpected weight loss can be associated with cancer, but also with a range of other conditions

• Weight loss codes in primary care typically represent ≥5% loss within a 6 month period, but there is a lack of evidence on how much weight loss and over what time period increase the likelihood of a cancer diagnosis in primary care

• Urgently refer people over the age of 60 years with unexpected weight loss for investigations to exclude cancer

• The optimal diagnostic strategy to detect cancer in patients with weight loss remains unclear

Differential diagnosis for patients with unexpected weight loss1

• Cardiovascular—End stage heart failure (cardiac cachexia)

• Endocrine—Adrenal insufficiency, diabetes, hyperthyroidism

• Gastrointestinal—Diarrhoea, colitis, malabsorption, mesenteric ischaemia

• Infection—Chronic infection (such as HIV, tuberculosis)

• Malignancy—Solid tumours more likely than haematological malignancies

• Medication—Antidepressants, antiepileptics, anxiolytics, diuretics, laxatives, stimulants

• Neurological—Dementia, multiple sclerosis, neuromuscular disease, Parkinson’s disease, stroke

• Psychiatric—Anorexia nervosa, anxiety, bulimia, depression

• Renal—End stage renal failure (uraemic cachexia)

• Respiratory—Chronic obstructive pulmonary disease (COPD), interstitial lung disease, vasculitis

• Rheumatologic—Rheumatoid arthritis

• Social—Excess alcohol consumption, neglect, use of opiates, poor oral health, poverty, smoking

Challenges in detecting weight loss in primary care