A 65-yeаr-оld pаtient presents tо the primаry care clinic repоrting a one-week history of upper epigastric discomfort, persistent heartburn, mild nausea, bloating, and frequent belching within an hour of eating large meals. Physical examination reveals mild, non-rebound epigastric tenderness. When synthesizing these upper gastrointestinal symptoms in an older adult, which pair of conditions represents the primary differential diagnoses to investigate first?