Can a healthy immune system destroy cancer cells?

Cancer development. Each of us humans has about ten tiny cancers at any given time. The fact that we do not all have clinically detectable tumors is due to the spectacular abilities of our immune systems. Only when a very smart tumor evades the immune system does it get big enough for us to call it cancer. Your immune system destroys cancer every day, and you can help it by feeding it healthy fruits and vegetables.
Yes. Most early changes that can progress to cancer are indeed detected and corrected by your healthy immune system. However, once cancer growth starts, your immune system can no longer contain the cancer and you will need medical/surgical treatment.