At diagnosis test for and, if found, treat H Pylori. This reduces the risk of gastric cancer by 50%.

NICE BNF: Helicobacter pylori infection

Taking aspirin has been shown to reduce the risk of bowel cancer by 50%. This is used off license but does form part of NICE and UKCGG guidelines. A patient information leaflet and prescribing information can be found here:

NICE: Lynch syndrome: should I take aspirin to reduce my chance of getting bowel cancer?

UK CGG: MLH1 guidelines

NICE BNF: aspirin

NICE: colorectal cancer

Lynch Syndrome: aspirin chemoprophylaxis infographic

Discuss prophylactic surgery with your patient and refer appropriately.