How might using antacids to mask heartburn inadvertently lead to more serious problems?

See below: Using antacids often for severe, frequent heartburn may mask inflamed esophagus, reflux disease, esophageal cancer. Frequent antacid use can cause milk-alkali syndrome: hypercalcemia, metabolic alkalosis (shift in body's acid-alkali balance), & renal insufficiency, kidney stones, & calcium deposits in tissues. Exacerbated by high doses of vitamin d which enhances calcium absorption.

Medicating heartburn: Making the symptoms go away with medication could make one forget that there's still a hiatal hernia. And non-acidic (symptom-free reflux) can still cause damage to the esophagus and can lead to precancerous changes therein (Barrett's esophagus). So even though you're on treatment, you need to undergo EGD every 2-3 years for surveillance purposes.