@judilafleur Molecular testing (which is a type of blood testing) for cancer comes in two main types: personalized tests like Natera Signatera and standardized tests like Northstar Response. (There are other companies, too.)

Personalized or "tumor-informed" tests like Natera's Signatera analyze the patient's specific tumor (from tumor tissue taken at the time of the initial biopsy, for example) to create a customized panel of 16 "targets" that looks for those exact mutations in blood samples. Standardized or "tumor-agnostic" tests like Northstar don't require tumor tissue samples and instead look for common cancer-associated genetic changes across many cancer types. >500 genomic loci, according to their website.

Both approaches detect tiny fragments of cancer DNA in the bloodstream, allowing doctors to monitor treatment effectiveness and potential recurrence earlier than imaging, but they differ in their precision (personalized tests are more sensitive for a specific cancer) versus versatility (standardized tests can detect multiple cancer types without needing tumor tissue). Given the increasing body of research demonstrating the tests' effectiveness, insurance companies now will often cover such testing, depending on the initial diagnosis (type of cancer, stage, etc.).