Question: Why can't our immune system fight efficiently against cancer?

Laura Garcia Ibanez answered on 16 Mar 2015:

Our immune system fights everyday against cancer. Everyday cancinogenic cells that eventually could cause cancer appear in our body due to mutations. They are detected by our immune system and killed. But sometimes, these cells are unnoticed to the immune system and that’s when the cancer appears. When our immune system is not able to detect these “bad cells” as bad, let them stay and don’t attack them. Cheers Asier!