This symptom should not be ignored. A weight loss of 5% in 6 months will have some pathology associated with the weight loss in 75-80% of cases. Malignancy may occur in up to 20% of cases. Weight loss associated with depression occurs in 10% of cases.
A systematic review was undertaken relating to weight loss and cancer risk (1):
- total of 25 studies were included, with 23 (92%) using primary care records
- of these, 20 (80%) defined weight loss as a physician’s coding of the symptom; the remainder collected data directly
- one defined unexplained weight loss using objective measurements
- positive associations between weight loss and cancer were found for 10 cancer sites:
- prostate, colorectal, lung, gastro-oesophageal, pancreatic, non-Hodgkin’s lymphoma, ovarian, myeloma, renal tract, and biliary tree
- sensitivity ranged from 2% to 47%, and specificity from 92% to 99%, across cancer sites
- positive predictive value for cancer in male and female patients with weight loss for all age groups >= 60 years exceeded the 3% risk threshold that current UK guidance proposes for further investigation
- risk with weight loss increases when it presents alongside another clinical feature suggesting an individual cancer site, and with increasing age
The study authors concluded that a primary care clinician's decision to code for weight loss is highly predictive of cancer. For such patients, urgent referral pathways are justified to investigate for cancer across multiple sites.