What are the key investigations to consider when evaluating a patient with unexplained weight loss and fatigue for possible malignancy?

When evaluating a patient with unexplained weight loss and fatigue for possible malignancy, consider the following investigations:

• Offer an urgent chest X-ray (to be done within 2 weeks) to assess for lung or mesothelioma, especially if the patient is over 40 and has symptoms such as fatigue, cough, shortness of breath, or chest pain ¹.
• Carry out tests in primary care, including measurement of serum CA125, particularly in women with unexplained weight loss and fatigue, to evaluate for ovarian cancer ¹.
• Consider a very urgent full blood count within 48 hours if there is persistent fatigue or unexplained fever, to assess for leukaemia or lymphoma ¹.
• In cases with associated abdominal symptoms, offer quantitative faecal immunochemical testing to evaluate for colorectal cancer ¹.