The problem of treatment resistant tumors in cancer research is complex but some new information might help. Researchers at the Institute for Cancer Research in the UK have found that tumors survive by stealing healthy blood vessels from surrounding tissue. Known as "angiogenesis" tumors are able to grow and spread if they have a fresh supply of healthy blood vessels. The way to keep this process going by stealing the surround vessels is called "vessel co-option" and before the recent study from the ICR the mechanism of how it happened was unclear.
A drug used in the study, sorafenib, became useless against angiogenesis after a while, so the team there experimented with "treatment holidays." Once patients were given a break from the drug, it started to work again when re-administered. The team at the ICR hopes this approach of stopping and starting treatment will be effective against liver cancer, breast cancer and bowel cancer.