Because it is derived from our own cells, it's difficult not only for the immune system to pick them out but for doctors to target the cancerous cells without damaging healthy ones in the process. One of the main areas of research when it comes to treating individual cancers is to try and identify certain markers that are only present on cancer cells. The researchers then try to either develop a drug to attack them or flag them up so that a person’s own immune cells can deal with them on their own.
But unfortunately, things are not even as simple as that. Different people respond to the same treatments differently. What works for one person to treat a specific variety of cancer will not necessarily work for another who has the same type of disease.
This is why people diagnosed with the disease are trialed with different regimes or combinations of treatments to see what is most effective for them. This touches on another aspect of the fight against cancer, in which some teams are working on genetically profiling patients' individual cancers to create a personalized treatment.
So, while we may never have a single cure for cancer, we’re certainly homing in on treating them. Some are easier to tackle than others and thus make bigger strides, but with more time and more research, we’re certainly getting there.