The association between unexpected weight loss and cancer diagnosis in primary care: a matched cohort analysis of 65,000 presentations

Background We aimed to understand the time period of cancer diagnosis and the cancer types detected in primary care patients with unexpected weight loss (UWL) to inform cancer guidelines. Methods This retrospective matched cohort study used cancer registry linked electronic health records from the UK's Clinical Practice Research Datalink from between 2000 and 2014. Univariable and multivariable time-to-event analyses examined the association between UWL, and all cancers combined, cancer site and stage. Results In all, 63,973 patients had UWL recorded, of whom 1375 (2.2%) were diagnosed with cancer within 2 years (days-to-diagnosis: mean 181; median 80). Men with UWL (HR 3.28 (2.88-3.73)) and women (1.87 (1.68-2.08)) were more likely than comparators to be diagnosed with cancer within 3 months. The association was greatest in men aged >= 50 years and women >= 70 years. The commonest cancers were pancreas, cancer of unknown primary, gastro-oesophageal, lymphoma, hepatobiliary, lung, bowel and renal-tract. The majority were late-stage, but there was some evidence of association with stage II and stage III cancers. In the 3-24 months after presenting with UWL, cancer diagnosis was less likely than in comparators. Conclusion UWL recorded in primary care is associated with a broad range of cancer sites of early and late-stage.