Could cutting one amino acid make rectal cancer treatment more effective?

This trial tests whether an arginine-free diet, given as a liquid formula for four weeks, can enhance the effects of standard chemoradiotherapy in people with locally advanced rectal cancer. The study first checks the diet's safety in a small group, then randomly assigns about 134 participants to receive either the diet plus chemoradiotherapy or chemoradiotherapy alone. The main goal is to see if the diet increases the chance of the tumor completely disappearing after treatment.