Mrs Medoway is a 55 year old teacher and attends the GP surgery with a 4 month history of reflux which has been resistant to Gaviscon and Ranitidine. Past medical history is unremarkable, and she quit smoking 20 years ago. She admits to eating healthy but is surprised to have lost 4kgs over the last 5 months, as she only joined the gym more recently. Abdominal examination today is unremarkable.
Based on the likely diagnosis, what is the most appropriate management step?