Can Chemotherapy Spread Cancer? Exploring the Evidence (2025)

Dr. Lee Cowden says most people don't die from cancer; they die from the side effects of treatment. While the "war against cancer" is moving toward more personalized and so-called "precision medicine" treatments, the old standby model of "cut, poison and burn," via surgery, chemotherapy and radiation, is still widely used and regarded as the standard of care for many cancer cases. One of the major problems with chemotherapy is its indiscriminate toxicity, which poisons your body systemically in an attempt to knock out cancer cells. There have long been signs that this model has fatal flaws and may cause more harm than good. In the case of the breast cancer chemotherapy drug Tamoxifen, for instance, patients must trade one risk for another, as while it may reduce breast cancer, it more than doubles women's risk of uterine cancer. (1) Serious, sometimes-fatal side effects (or more aptly, simply effects) of chemotherapy are common, as are serious unf...